Wireless communication system, wireless base station, wireless terminal, and wireless communication method

ABSTRACT

A wireless base station, includes: a wireless transceiver configured to transmit to a wireless terminal a downlink frame including a downlink control information, the wireless downlink control information includes information representing a specified offset, wherein the wireless transceiver is further configured to receive an uplink frame from the wireless terminal; and a processor circuit coupled to the wireless transceiver and configured to determine uplink control information from the uplink frame, the uplink control information being offset by at least the specified offset from a location in the uplink frame that is the same as a location where the downlink control information was located in the downlink frame.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 14/487,664, filed Sep. 16, 2014, which is a continuation applicationof International Application No. PCT/JP2012/001907, filed on Mar. 19,2012, the entire contents of each are incorporated herein by reference.

FIELD

The present invention relates to a wireless communication system, awireless terminal, a wireless base station, and a wireless communicationmethod.

BACKGROUND

In recent years, in an attempt to further increase speed and capacity ofwireless communication in a wireless communication system, such as amobile phone system (cellular system), discussions are held on wirelesscommunication technology for the next generation. For example, in the3GPP (3rd generation partnership project), which is a standardsorganization, a communication standard called as LTE (long termevolution) and a communication standard called as LTE-A (LTE-advanced)based on the wireless communication technique of LTE are suggested.

The latest communication standard completed in the 3GPP is Release 10compatible with LTE-A, in which Releases 8 and 9 compatible with LTE aregreatly functionally enhanced. Currently, discussions are held forcompletion of Release 11, in which Release 10 is further enhanced. Inthe descriptions below, “LTE” includes, in addition to LTE and LTE-A,other wireless communication systems that are made by enhancing LTEunless otherwise noted.

In Release 11 of the 3GPP, coordinated multiple point (CoMP) is one ofthe techniques that are discussed actively in particular. Simply put,CoMP is a technique to coordinate sending and receiving to a wirelessterminal (UE: user equipment) between different wireless base stations(eNB: evolved node B). In the following descriptions, a wireless link ina direction from a wireless terminal to a wireless base station iscalled as an uplink (UL) and a wireless link in a direction from awireless base station to a wireless terminal is called as a downlink(DL).

There are several forms of CoMP, and a scenario is known in which awireless terminal carries out communication with different wireless basestations for UL and DL. In a regular case, a wireless terminal carriesout communication with an identical wireless base station for UL and DL.That is, it is common that a wireless terminal carries out communicationwith a connected wireless base station (serving cell). As an example, awireless terminal receives UL scheduling information from a connectedwireless base station on a DL and sends data to the connected wirelessbase station on a UL based on the received UL scheduling information. Asanother example, a wireless terminal receives data from a connectedwireless base station on a DL and sends a response signal (ACK signal orNACK signal) to the received data to the connected wireless base stationon a UL.

However, there is sometimes another wireless base station whosecommunication quality of UL for the wireless terminal is higher than theconnected wireless base station. Even when certain communication qualityof DL (receiving quality, propagation delay, and the like) is secured,in such a case that a wireless terminal is located at a cell edge, thecommunication quality of UL may not be good. When there is anotherwireless base station whose communication quality of DL is higher thanthe connected wireless base station, the connected wireless base stationof the wireless terminal is switched by handover, so that this is out ofthe problem.

Such problem easily occurs as well in a so-called heterogeneous network,for example, where macrocells, which are regular base stations, andpicocells and the like (also microcells, femtocells, and the like),which are small base stations, are mixed. In a heterogeneous network, apicocell is desired to suppress the DL cell size (suppress the sendingpower) in order to inhibit interference in a macrocell. That is, amacrocell and a picocell greatly differ in DL cell size (sending power).Therefore, a situation may occur that, for a wireless terminal locatedat a cell edge of the connected macrocell, the DL quality is better witha macrocell while the UL quality is better with a picocell.

In the 3GPP, in view of such problems, a scenario is under review inwhich a wireless terminal carries out communication with differentwireless base stations for UL and DL as described above. In thisscenario, when there is another wireless base station whosecommunication quality of UL for a wireless terminal is higher than theconnected wireless base station, the wireless terminal carries out ULcommunication with the base station different from the connectedwireless base station. As an example, it is possible that the wirelessterminal receives UL scheduling information from the connected wirelessbase station on a DL and sends data to a base station different from theconnected wireless base station on a UL based on the received ULscheduling information. As another example, it is possible that awireless terminal receives data from the connected wireless base stationon a DL and sends a response signal to the received data to a basestation different from the connected wireless base station on a UL. Insuch a manner, it becomes possible to secure the UL wirelesscommunication quality to a wireless terminal that has poor UL wirelessquality with the connected wireless base station. Then, as a result, aneffect of improving transmission efficiency of the entire system isexpected.

Non Patent Literatures 3GPP TS36.211 V10.4.0 (2011 December), 3GPPTS36.213 V10.4.0 (2011 December), 3GPP TR36.814 V9.0.0 (2010 March),3GPP TR36.819 V11.0.0 (2011 September), 3GPP R1-114324 “On ReferenceSignal Enhancements for UL CoMP” (2011 November) are examples of therelated art.

SUMMARY

According to an aspect of the invention, a wireless communication systemincludes a wireless base station, and a wireless terminal configured toreceive from the wireless base station a downlink frame including dataand a downlink control signal for decoding the data, the downlinkcontrol signal being mapped to a first downlink control resource elementof downlink control resource elements that are resource units used fortransmissions of downlink control signals in the downlink frame, and totransmit an uplink frame including an uplink control signal foracknowledging a decoding result of the data, the uplink control signalbeing mapped to a first uplink control resource element of uplinkcontrol resource elements that are resource units used for transmissionsof uplink control signals in the uplink frame, the first uplink controlresource element being determined by shifting a second uplink controlresource element of the uplink control resource elements by an offsetnumber whose unit is one of the uplink control resource elements, thesecond uplink control resource element being determined based on alocation of the first downlink control resource element in the downlinkframe, the offset number being determined based on a first offsetinformation included in the downlink control signal.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating problems in conventional techniques.

FIG. 2 is a diagram illustrating one example of a network configurationof a wireless communication system in a first embodiment.

FIG. 3 is one example of a process sequence diagram of the wirelesscommunication system in the first embodiment.

FIG. 4 is a diagram illustrating one example of a DCI format in thewireless communication system of the first embodiment.

FIG. 5 is one example of a functional configuration diagram of awireless base station in the wireless communication system of the firstembodiment.

FIG. 6 is one example of a functional configuration diagram of awireless terminal in the wireless communication system of the firstembodiment.

FIG. 7 is one example of a hardware configuration diagram of thewireless base station in the wireless communication system of the firstembodiment.

FIG. 8 is one example of a hardware configuration diagram of thewireless terminal in the wireless communication system of the firstembodiment.

FIG. 9 is one example of a process sequence diagram of a wirelesscommunication system in a second embodiment.

FIG. 10 is a diagram illustrating one example of a DCI format in thewireless communication system of the second embodiment.

FIG. 11 is one example of a process sequence diagram of a wirelesscommunication system in a third embodiment.

FIG. 12 is one example of a process sequence diagram of a wirelesscommunication system in a fourth embodiment.

FIG. 13 is one example of a process sequence diagram of a wirelesscommunication system in a fifth embodiment.

FIG. 14 is one example of a process sequence diagram of a wirelesscommunication system in a sixth embodiment.

FIG. 15A is a diagram illustrating one example of a DCI format in awireless communication system of a seventh embodiment.

FIG. 15B is a diagram illustrating one example of a DCI format in awireless communication system of a seventh embodiment.

DESCRIPTION OF EMBODIMENTS

When a wireless terminal and a wireless base station carry outcommunication, with some exceptions, scheduling of a wireless resource(hereinafter, may be referred to simply as scheduling) is carried out.Scheduling of a wireless resource is to determine a wireless resourcethat is used for sending and receiving of a wireless signal (to assign awireless resource or to determine allocation of a wireless resource issynonymous). For example, a wireless resource is defined by a timecomponent and a frequency component. Scheduling of a wireless resourceis carried out by a connected wireless base station to a subordinatewireless terminal. The connected wireless base station notifies aconnected wireless terminal of scheduling information related to thedetermined scheduling on a DL, and the connected wireless terminal andthe wireless base station carry out sending and receiving of a wirelesssignal based on the scheduling information.

Consideration is given to the above described scheduling in the scenariowhere a wireless terminal carries out communication with differentwireless base stations for UL and DL. Now, it is assumed that a wirelessterminal is intended to send data on a UL. At this time, the wirelessterminal sends a signal that requests UL scheduling to the connectedwireless base station. Next, it is assumed that the connected wirelessbase station that has received the signal that requests UL schedulingdetermines to cause another wireless base station to receive UL data ofthe wireless terminal based on receiving quality of the wireless signalfrom the wireless terminal and the like.

At this time, the connected wireless base station sends UL schedulinginformation to the wireless terminal on a DL. The wireless terminalsends a wireless signal including UL data using a UL wireless resourcethat is specified by the received UL scheduling information.

Meanwhile, in parallel with the above, the connected wireless basestation sends the UL scheduling information also to another wirelessbase station via a backhaul network (network that links between wirelessbase stations and a wireless base station with a core network). Theother wireless base station receives a wireless signal including UL datafrom the wireless terminal using the wireless resource that is specifiedby the received UL scheduling information.

According to the above consideration, in the scenario where a wirelessterminal carries out communication with different wireless base stationsfor UL and DL, it may also be considered that scheduling is carried outwithout a problem and the other wireless base station is capable ofreceiving data from the wireless terminal. However, in such scenario, aphenomenon is confirmed in which another wireless base station differentfrom the connected base station is sometimes not capable of receivingdata from the wireless terminal.

The disclosed technique has made in view of the above, and it is anobject thereof to provide a wireless communication system, a wirelessterminal, a wireless base station, and a wireless communication methodthat allow, when a wireless terminal carries out communication withdifferent wireless base stations for UL and DL, another wireless basestation different from the connected base station to receive data fromthe wireless terminal.

Descriptions are given below to embodiments of a wireless communicationsystem, a wireless terminal, a wireless base station, and a wirelesscommunication method of the disclosure, with reference to the drawings.Although descriptions are given as separate embodiments for convenience,it is of course possible to also obtain effects of combination bycombining respective embodiments and further enhance the usability.

[a] Identification of Problem

As described above, in the scenario where a wireless terminal carriesout communication with different wireless base stations for UL and DL, aphenomenon is confirmed in which another wireless base station differentfrom the connected base station is sometimes not capable of receivingdata from the wireless terminal. Keenly reviewing this phenomenon, theinventor has found that there are problems of wireless resourcescheduling in the scenario. Here, before describing the respectiveembodiments, descriptions are given to identification of the problemsthat the inventor has found.

As described above, a wireless terminal sends a wireless signalincluding UL data (called as a first wireless signal) using a wirelessresource that is specified by UL scheduling information received fromthe connected wireless base station. In contrast, another wireless basestation receives a wireless signal including UL data from the wirelessterminal based on scheduling information received from the connectedwireless base station (that is, based on a wireless resource defined bythe connected wireless base station). However, at this time, there is apossibility that the other wireless base station has already sent thescheduling information specifying the wireless resource to anotherwireless terminal connected thereto. This is because it is not possiblefor the other wireless base station to predict a UL reception requestfrom the connected wireless base station in advance.

In such a case, the other wireless terminal sends a wireless signalincluding data (called as a second wireless signal) to the otherwireless base station using the wireless resource specified by the ULscheduling information received from the other wireless base station.Thus, the wireless terminal and the other wireless terminal turn out tocarry out UL sending using same wireless resources (sending time,sending frequency). In other words, the first wireless signal and thesecond wireless signal are sent on same wireless resources. As a result,conflict occurs in a UL wireless resource. Since the first wirelesssignal and the second wireless signal include different data andinterfere with each other, it becomes difficult for the other wirelessbase station to decode any data. Accordingly, in such a case, the otherwireless base station turns out not to be capable of receiving datawithout an error from the wireless terminal. FIG. 1 illustrates anoutline of this problem.

To sum up above, in the scenario where a wireless terminal carries outcommunication with different wireless base stations for UL and DL,conflict of a wireless resource may occur in UL sending. Then, whenconflict of a wireless resource occurs in UL sending, it is not possiblethat another wireless base station different from the connected basestation receives data without an error from the wireless terminal.Accordingly, in the scenario where a wireless terminal carries outcommunication with different wireless base stations for UL and DL, thereis a problem that the other wireless base station is sometimes notcapable of receiving data from the wireless terminal.

In addition, when the other wireless base station is not capable ofreceiving data without an error (not capable of decoding data), thewireless terminal and the other wireless terminal turn out to carry outresending of data in response to reception of a NACK signal or a timeoutof a response signal. Resending of data leads to a waste of wirelessresources and thus is not preferred.

The technique of the disclosure has been embodied based on the findingsof the above problems by the inventor.

[b] First Embodiment

FIG. 2 illustrates a network configuration of a wireless communicationsystem in the first embodiment. The present embodiment is an embodimentof a wireless communication system compliant with LTE. Therefore, someof LTE specific terms and concepts appear. However, the presentembodiment is merely one example and it is noted that it is applicableto a wireless communication system compliant with a communicationstandard other than LTE.

The wireless communication system illustrated in FIG. 2 is provided witha plurality of wireless base stations (eNB: evolved node B) 1 a, 1 b, 1c, wireless terminals (UE: user equipment) 2 a, 2 b, and the like. Inthe descriptions below, the plurality of wireless base stations 1 a, 1b, 1 c may be represented collectively as wireless base stations 1. Inaddition, the plurality of wireless terminals 2 a, 2 b may berepresented collectively as wireless terminals 2.

Wireless networks between the wireless base stations and the wirelessterminals are called as wireless access networks. The wireless basestations 1 are connected with a wired or wireless network (transmissionnetwork) called as a backhaul network. A backhaul network is a networkthat links between the wireless base stations 1 and the wireless basestations 1 with a core network. The wireless base stations 1 are capableof carrying out communication with a device connected to the corenetwork via the backhaul network. To the core network, an MME (mobilitymanagement entity), an SAE-GW (system architecture evolution gateway),and the like that are not illustrated are connected. An LTE network mayalso be called as an EPS (evolved packet system). The EPS includes aeUTRAN (evolved universal terrestrial radio network), which is awireless access network, and an EPC (evolved packet core), which is acore network. The core network may also be called as an SAE (systemarchitecture evolution).

The wireless base stations 1 (may also be called simply as basestations) in FIG. 2 is a device that carries out wireless communicationwith the wireless terminals 2 via the wireless access network and alsois connected to the backhaul network. The wireless base station 1 acarries out sending and receiving of data with the subordinate wirelessterminal 2 a (may be referred to as a connected wireless terminal) andalso carries out a variety of control over the wireless terminal 2 a byexchanging various types of control information with the subordinatewireless terminal 2 a. In addition, the wireless base station 1 acarries out relay of data with the other wireless base stations 1 b, 1c, each other, via the backhaul network and also is capable ofcooperation by exchanging various types of control information with theother wireless base stations 1 b, 1 c.

The wireless base stations 1 carries out exchange of a variety ofcontrol information with a control device, such as an MME connected tothe core network beyond the backhaul network, via the backhaul network.In addition, the wireless base station 1 a relays the data received fromthe subordinate wireless terminal 2 a to a relay device, such as anSAE-GW connected to the core network, and also relays the data receivedfrom the relay device, such as an SAE-GW, to the subordinate wirelessterminal 2 a.

The wireless base stations 1 may be connected with the backhaul networkby wire and may also be connected wirelessly. In addition, the wirelessbase stations 1 may also have a communication function with the wirelessaccess network as an extended RRH, which is a separate device, andconnect by wire therewith.

Although a “cell” is a range that the wireless base stations 1 covers inorder that the wireless terminals 2 sends and receives a wireless signal(strictly, there are UL cells and DL cells), the wireless base stations1 and the cell are almost corresponding concepts, so that it does notmatter if the “cell” and the “wireless base station” are readinterchangeably as appropriate in the descriptions below.

Meanwhile, the wireless terminals 2 (may also be called simply asterminals; may also be called as user devices, subscriber stations,mobile stations, and the like) in FIG. 2 are devices that carry outwireless communication with the wireless base stations 1 via thewireless access network. The wireless terminal 2 a is connected to onewireless base station 1 a, and as a change occurs in a wireless state bytransfer and the like, the wireless base station 1 to be connected isswitched by handover. Here, while “connection” indicates that a wirelessterminal is registered in (attached to) a wireless base station, it mayalso be interpreted to simply mean in communication. The wireless basestation 1 a connected by the wireless terminal 2 a is called as aconnected wireless base station or a serving cell. The wireless terminal2 a carries out sending and receiving of data by wireless communicationwith the connected wireless base station 1 a and also is subject to avariety of control by exchanging various types of control information bywireless communication with the connected wireless base station 1 a.

The wireless terminal 2 a in the present embodiment receives a DLwireless signal from the connected wireless base station 1 a. Thewireless terminal 2 a in the present embodiment is capable of sending aUL wireless signal to the connected wireless base station 1 a or theother wireless base stations 1 b, 1 c. Accordingly, the wirelessterminal 2 a in the present embodiment is capable of carrying outcommunication with wireless base stations 1 different for DL and UL.Details are described later.

The wireless communication system in the present embodiment isconfigured with, as well as a DL wireless signal and a UL wirelesssignal, a wireless frame (may also be referred to simply as a frame)having a predetermined length (for example, 10 milliseconds). Further,one wireless frame is respectively configured with a predeterminednumber (for example, 10) of wireless subframes (may also be referred tosimply as subframes) having a predetermined length (for example, 1millisecond). Then, each subframe is further divided into each physicalchannel, which is a physical communication path. Since a “frame” and a“subframe” are merely terms that indicate processing units of a wirelesssignal, these terms may also be read interchangeably as appropriate inthe following.

As a DL physical channel, there are a downlink shared channel (PDSCH:physical downlink shared channel) that is used for transmission of a DLdata signal and the like, a downlink control channel (PDCCH: physicaldownlink control channel) that is used for transmission of a DL controlsignal, and the like. In a PDSCH, as well as a DL data signal, a DLreference signal for various types of measurement and the like are alsomapped. Meanwhile, as a UL physical channel, there are an uplink sharedchannel (PUSCH: physical uplink shared channel) that is used fortransmission of a UL data signal and the like, an uplink control channel(PUCCH: physical uplink control channel) that is used for transmissionof a UL control signal, and the like. In PUSCH, as well as a UL datasignal, a UL reference signal for various types of measurement and thelike are also mapped.

Next, based on FIG. 3, descriptions are given to a process sequence ofthe wireless communication system in the first embodiment. FIG. 3 is aprocess sequence when sending data (UL data) to the connected wirelessbase station 1 a occurs in the wireless terminal 2 a. As describedbefore, the wireless terminal 2 a in the present embodiment is capableof receiving a DL wireless signal from the connected wireless basestation 1 a and also sending a UL wireless signal to the connectedwireless base station 1 a or the other wireless base station 1 b, whichis another wireless base station. That is, the wireless terminal 2 a iscapable of carrying out communication with wireless base stations 1different for DL and UL. FIG. 3 is one example of such asymmetricwireless communication.

In S101 in FIG. 3, UL data occurs in the wireless terminal 2 a. Forexample, UL data occurs when an audio signal, data, and the like aresent from the wireless terminal 2 a to the other wireless terminal 2 b,when an application on the wireless terminal 2 a sends data to a serveron the Internet, and the like. As the UL data occurs, in S102, thewireless terminal 2 a sends UL schedule requesting information, which isinformation to request a UL wireless resource in order to send the ULdata, to the connected wireless base station 1 a on a UL wirelesssignal. In the UL schedule requesting information, informationindicating a UL wireless resource amount to be used (UL wirelessresource amount information) is stored.

As receiving the UL schedule requesting information, the connectedwireless base station 1 a starts scheduling of a UL wireless resource tothe wireless terminal 2 a. The connected wireless base station 1 afirstly obtains, for example, UL receiving quality from the wirelessterminal 2 a. It is possible to obtain the UL receiving quality based ona sound reference signal (SRS) included in the UL wireless signal. Then,the connected wireless base station 1 a decides whether the obtained ULreceiving quality satisfies a predetermined criterion. Based on thisdecision, in S103, the connected wireless base station 1 a determineswhether or not to set a base station to receive UL data as a localstation (connected wireless base station 1 a). When the receivingquality satisfies the predetermined criterion, the connected wirelessbase station 1 a determines the base station to receive UL data as thelocal station (connected wireless base station 1 a). In contrast, whenthe receiving quality does not satisfy a predetermined criterion, theconnected wireless base station 1 a determines the base station toreceive UL data as any of the other wireless base stations 1 b, 1 cother than the local station (at this time point, the other wirelessbase stations 1 b, 1 c do not have to be determined into one). This isbecause, when the UL receiving quality from the wireless terminal 2 a inthe connected wireless base station 1 a is poor, it is possible tosecure communication efficiency of the entire system more by causing theUL data from the wireless terminal 2 a to be received by the otherwireless base stations 1 b, 1 c.

Although the connected wireless base station 1 a in this example carriesout determination of whether or not to receive at a local station inS103 based on the UL receiving quality, instead of or in addition tothis, the determination may also be carried out based on another index.For example, when the UL wireless resource use amount or activity rateof the local station is not less than the predetermination (when thereare less space in the UL wireless resource), it is possible that theconnected wireless base station 1 a determines the base station toreceive UL data as other than the local station.

Back to the description of FIG. 3, in this example, it is assumed thatthe connected wireless base station 1 a determines, in S103, the basestation to receive UL data as other than the local station (connectedwireless base station 1 a). At this time, in S104, the connectedwireless base station 1 a sends wireless resource requestinginformation, which is information to request a UL wireless resource tothe other wireless base stations 1 b, 1 c via the transmission network.Here, the connected wireless base station 1 a is capable of carrying outselection of a sending destination of the wireless resource requestinginformation based on, for example, DL receiving quality of each wirelessbase station stored in a measurement report, not illustrated, that issuccessively received from the wireless terminal 2 a. The other wirelessbase stations 1 b, 1 c to be the sending destination of wirelessresource requesting information may be one or a plurality, and in theexample of FIG. 3, it is assumed that two other wireless base stations 1b, 1 c are selected as the sending destination.

In S105 in FIG. 3, as receiving the wireless resource requestinginformation respectively, the other wireless base stations 1 b, 1 cobtain unused wireless resources. Here, for example, an unused wirelessresource in the other wireless base station 1 b is a UL wirelessresource that the other wireless base station 1 b does not cause anysubordinate wireless terminal 2 b to use for UL sending (not to bescheduled for UL sending). In other words, even when the wirelessterminal 2 a subordinate to the connected wireless base station 1 acarries out UL sending using an unused wireless resource to the otherwireless base station 1 b, resource conflict turns out not to occur.Since the other wireless base station 1 b controls and manages schedulesof all subordinate wireless terminals 2 b, it is possible to obtain theunused wireless resources easily. In S106, the other wireless basestations 1 b, 1 c respectively send other station wireless resourceinformation including unused wireless resources information thatindicates the obtained unused wireless resources to the connectedwireless base station 1 a via the transmission network.

The connected wireless base station 1 a receives the other stationwireless resource information including the unused wireless resourcesinformation respectively from the other wireless base stations 1 b, 1 c.Then, in S107, the connected wireless base station 1 a determines a ULwireless resource (referred to as a determined wireless resource) thatis used for UL sending from the subordinate wireless terminal 2 a andthe other wireless base station (referred to as a determined wirelessbase station) to be a sending destination of the UL sending based on thereceived unused wireless resources information. Here, it is assumed thatthe magnitude of the determined wireless resources is not less than theUL wireless resource amount requested in the UL schedule requestinginformation from the wireless terminal 2 a. In S107, the connectedwireless base station 1 a is capable of determining the determinedwireless resource and the determined wireless base station by anarbitrary criterion based on the unused wireless resources indicated bythe unused wireless resources information. For example, it is possiblethat the connected wireless base station 1 a selects arbitrary one fromthe unused wireless resources capable of securing the requested ULwireless resource amount to determine the determined wireless resourcetherefrom. Then, the connected wireless base station 1 a is capable ofsetting the other wireless base station 1 b that has sent the selectedunused wireless resource (information) as the determined wireless basestation. Here, it is assumed that the connected wireless base station 1a determines the determined wireless resource from the unused wirelessresources that the other wireless base station 1 b has sent anddetermines the other wireless base station 1 b as the determinedwireless base station.

In S108, the connected wireless base station 1 a sends informationindicating the determined wireless resource determined in S107 (referredto as determined wireless resource information) to the subordinatewireless terminal 2 a on a DL wireless signal. Here, this DL wirelesssignal includes DCI (data control information), which is a DL controlsignal defined by LTE. DCI is a DL control signal including controlinformation, such as information related to data scheduling, used by thewireless terminal 2 a for sending and receiving of data. There areseveral formats in DCI, and a control object is different depending onthe format. For example, format 0 in DCI is to control over the PUSCH,that is, UL data. Formats 1A, 1B, 1C, 1, 2 are respectively to controlover the PDSCH, that is, DL data.

FIG. 4 illustrates one example of a DCI format in the first embodiment.The DCI illustrated in FIG. 4 is defined by LTE, and it is used as is inthe first embodiment. The DCI in FIG. 4 includes an RNTI (radio networktemporary identifier), which is an identifier of a DCI destination(wireless terminal 2 a), RB assignment (resource block assignment),which is information indicating the wireless resource having dataallocated thereto (to which resource block (RB) on the wireless framedata is assigned), and MCS (modulation and coding scheme), whichindicates modulation and coding scheme of data. Although DCI includes,as well as these, parameters, such as an RV (redundancy version), an NDI(new data indicator), a HARQ (hybrid automatic repeat request)processing number, and PUCCH power control, details are omitted.

In the present embodiment, the determined wireless resource informationcorresponds to the RB assignment of DCI. That is, in S108, the connectedwireless base station 1 a in the present embodiment sends the determinedwireless resource information to the subordinate wireless terminal 2 aby sending the DCI on a DL wireless signal. In contrast, in S108, thewireless terminal 2 a receives the DL wireless signal including the DCIthat includes the determined wireless resource information (RBassignment). At this time, the wireless terminal 2 a recognizes(detects) the DCI towards itself based on the RNTI included in the DCI.In addition, the wireless terminal 2 a recognizes (detects) that the DCItargets the UL data based on the DCI format.

In S109 in FIG. 3, the connected wireless base station 1 a sends thedetermined wireless resource information to the other wireless basestation 1 b, which is the determined wireless base station determined inS107 via the transmission network. The connected wireless base station 1a in the present embodiment sends the determined wireless resourceinformation to the other wireless base station 1 b, which is thedetermined wireless base station, by sending the DCI in S109. Here, S108and S109 may also be simultaneous or opposite in order. This completesscheduling of UL wireless sending from the subordinate wireless terminal2 a to the other wireless base station 1 b by the connected wirelessbase station 1 a. When the connected wireless base station 1 adetermines the base station to receive UL data as the local station inS103, regular UL wireless resource scheduling may be carried out, sothat the description is omitted.

Subsequently, in S110 in FIG. 3, the wireless terminal 2 a sends a ULwireless signal including the UL data using the UL wireless resourceindicated by the received determined wireless resource information (RBassignment of DCI). At this time, the wireless terminal 2 a carries outcoding and modulation of the UL data based on an MCS included in the DCIreceived in S108. In contrast, in S110, the other wireless base station1 b receives the UL wireless signal sent by the wireless terminal 2 ausing the UL wireless resource indicated by the received determinedwireless resource information. At this time, the other wireless basestation 1 b carries out demodulation and decoding of the UL data basedon the MCS included in the DCI received in S109. Lastly, in S111, theother wireless base station 1 b sends (transfers) the UL data includedin the received UL wireless signal to the connected wireless basestation 1 a via the transmission network. This completes reception ofthe UL data in S112.

As described above, in the wireless communication system of the firstembodiment, the connected wireless base station 1 a receives the otherstation wireless resource information including the unused wirelessresources information, which is information indicating UL wirelessresources not used by the other wireless base station 1 b, from theother wireless base station 1 b. Then, the connected wireless basestation 1 a schedules the UL wireless resource used for UL sending fromthe subordinate wireless terminal 2 a to the other wireless base station1 b based on the received unused wireless resources information. Thus,it is possible to avoid conflict in the UL wireless resource between theUL sending from the wireless terminal 2 a subordinate to the connectedwireless base station 1 a to the other wireless base station 1 b and theUL sending from another wireless terminal 2 a subordinate to the otherwireless base station 1 b to the other wireless base station 1 b.Accordingly, according to the wireless communication system in the firstembodiment, when the wireless terminal 2 a carries out communicationwith different wireless base stations for UL and DL, it is possible thatthe other wireless base station different from the connected basestation receives data from the wireless terminal. In addition, as aresult, it is possible to achieve efficient utilization of wirelessresources.

Next, based on FIG. 5 and FIG. 6, descriptions are given to functionalconfiguration of each device in the first embodiment in order.

FIG. 5 is a diagram illustrating one example of functional configurationof the wireless base station 1 in the first embodiment. The wirelessbase station 1 is provided with, for example, a UL wireless receivingunit 101, a UL frame analysis unit 102, a UL reference signal processingunit 103, a UL control signal demodulation and decoding unit 104, a ULdata signal demodulation and decoding unit 105, a scheduler unit 106, aDL data signal generation unit 107, a DL data signal coding andmodulation unit 108, a DL control signal generation unit 109, a DLcontrol signal coding and modulation unit 110, a DL reference signalgeneration unit 111, a DL frame generation unit 112, a DL wirelesssending unit 113, a transmission network sending unit 114, and atransmission network receiving unit 115.

Firstly, descriptions are given to each of these functions in theconnected wireless base station 1 a of the first embodiment.

The UL wireless receiving unit 101 receives a UL wireless signal,downconverts the received wireless signal by frequency conversion andthe like for conversion to a baseband signal corresponding to a ULframe, and outputs it to the UL frame analysis unit 102. The UL frameanalysis unit 102 extracts a UL data signal, a UL control signal, and aUL reference signal from the baseband signal corresponding to the ULframe. At this time, the UL frame analysis unit 102 carries outextraction of each signal based on UL scheduling information(information equivalent to RB assignment of DCI) inputted from thescheduler unit 106. Then, the UL frame analysis unit 102 outputs the ULreference signal to the UL reference signal processing unit 103, outputsthe UL control signal to the UL control signal demodulation and decodingunit 104, and outputs the UL data signal to the UL data signaldemodulation and decoding unit 105.

The UL reference signal processing unit 103 obtains UL channelcharacteristics based on a demodulation reference signal (DM-RS) amongthe UL reference signal and inputs them to the UL control signaldemodulation and decoding unit 104 and the UL data signal demodulationand decoding unit 105. In addition, the UL reference signal processingunit 103 obtains UL receiving quality based on a sounding referencesignal (SRS), which is a reference signal for scheduling, among the ULreference signal and inputs it to the scheduler unit 106.

The UL control signal demodulation and decoding unit 104 demodulates theUL control signal to carry out error correction and decoding. The ULcontrol signal demodulation and decoding unit 104 carries outdemodulation and decoding of the UL control signal using the UL channelcharacteristics inputted from a UL reference signal generation unit 212and predetermined modulation scheme and error correction and codingscheme. The UL control signal demodulation and decoding unit 104 inputsthe demodulated and decoded UL control signal to the scheduler unit 106.As examples of the UL control signal, there are UL schedule requestinginformation, a UL response signal (ACK/NACK signal) to DL data, and thelike.

The UL data signal demodulation and decoding unit 105 demodulates the ULdata signal to carry out error correction and decoding. The UL datasignal demodulation and decoding unit 105 carries out demodulation anddecoding of the UL data signal using the UL channel characteristicsinputted from the UL reference signal generation unit 212 and themodulation scheme and the error correction and coding scheme inputtedfrom the scheduler unit 106. The UL data signal demodulation anddecoding unit 105 inputs the demodulated and decoded UL data signal tothe scheduler unit 106.

Descriptions are given to the scheduler unit 106 in the presentembodiment. The scheduler unit 106 carries out scheduling of a wirelessresource used for wireless communication and also carries out a varietyof control associated with the scheduling of a wireless resource. Thescheduler unit 106 schedules respective UL and DL wireless resources. Asa first example, when UL schedule requesting information, which is oneitem of the UL control information sent by the wireless terminal 2 a, isinputted from the UL control signal demodulation and decoding unit 104,the scheduler unit 106 schedules a UL wireless resource to the wirelessterminal 2 a. As a second example, in such a case that a DL schedulerequisition is inputted from an upper layer unit 206 (a case that datahas to be sent to the wireless terminal 2 a on a DL), the scheduler unit106 schedules a DL wireless resource.

Here, when scheduling a UL wireless resource to the wireless terminal 2a, the scheduler unit 106 in the present embodiment selectivelydetermines the wireless base station 1 to be a UL sending destination.In other words, the scheduler unit 106 in the present embodiment iscapable of selecting the other wireless base stations 1 b, 1 c otherthan the local station (wireless base station 1 a) as the UL sendingdestination. Of course, it goes without saying that the scheduler unit106 may also select the local station (wireless base station 1 a) as theUL sending destination. The scheduler unit 106 may employ a variety ofmethods in determination of the wireless base station 1 to be the ULsending destination of the wireless terminal 2 a and determination ofthe UL wireless resource to be assigned to the wireless terminal 2 a.The scheduler unit 106 may also carry out these determinationscollectively and may also carry out them in order.

Descriptions are given to scheduling of a UL wireless resource when thescheduler unit 106 in the present embodiment selects the other wirelessbase station 1 b as the UL sending destination from the wirelessterminal 2 a. In this case, the scheduler unit 106 has to avoid theconflict in a UL wireless resource described above. With that, whenselecting the other wireless base station 1 b as the UL sendingdestination, the scheduler unit 106 obtains information related to theUL wireless resource used by the wireless terminal 2 a subordinate tothe other wireless base station 1 b (hereinafter, may also be referredto as other station wireless resource information). This point is one ofthe processes that conventional techniques do not perform, so thatdetailed descriptions are given below.

Descriptions are given to contents of the other station wirelessresource information in the present embodiment. The contents of theother station wireless resource information may be, as an example,information indicating a UL wireless resource not used by the otherwireless base station 1 b (referred to as unused wireless resourcesinformation). The unused wireless resources information is, so to speak,information indicating a wireless resource where resource conflict doesnot occur even when being used by the wireless base station 1 a (evenwhen being scheduled as the UL wireless resource used in UL sending fromthe wireless terminal 2 a subordinate to the wireless base station is tothe other wireless base station 1 b). It becomes possible to avoid ULresource conflict by that the scheduler unit 106 of the connectedwireless base station 1 a selectively determines the UL wirelessresource to be assigned to the subordinate wireless terminal 2 a fromthe unused wireless resources information received from the otherwireless base station 1 b.

The unused wireless resources information is merely one example of theother station wireless resource information. As another example of theother station wireless resource information, information indicating a ULwireless resource used by the other wireless base station 1 b (referredto as used wireless resource information) is also available. The usedwireless resource information is, so to speak, information indicating awireless resource where resource conflict occurs when being used by thewireless base station 1 a (when being scheduled as the UL wirelessresource used in the UL sending from the wireless terminal 2 asubordinate to the wireless base station to the other wireless basestation 1 b). It becomes possible to avoid UL resource conflict by thatthe scheduler unit 106 of the wireless base station 1 a selectivelydetermines the UL wireless resource to be assigned to the subordinatewireless terminal 2 a from the UL wireless resource other than the usedwireless resource information received from the other wireless basestation 1 b.

Descriptions are given to a procedure where the connected wireless basestation 1 a of the present embodiment obtains the other station wirelessresource information from the other wireless base stations 1 b, 1 c. Inthe procedure where the wireless base station obtains the other stationwireless resource information, the scheduler unit 106 carries out, forexample, sending of requesting information (referred to as wirelessresource requesting information) that requests other station wirelessresource information to the other wireless base stations 1 b, 1 c.Specifically, it goes as follows, for example. Firstly, when the ULreceiving quality inputted from the UL reference signal unit is lowerthan a predetermined value, the scheduler unit 106 determines to sendwireless resource requesting information. Next, the scheduler unit 106sends wireless resource requesting information to the other wirelessbase stations 1 b, 1 c (adjacent wireless base or peripheral wirelessbase station). The other wireless base stations 1 b, 1 c to be thesending destination may be one or may also be a plurality. In addition,it is possible to carry out the selection of the other wireless basestations 1 b, 1 c to be the sending destination based on, for example,DL receiving quality information for each wireless base station that isstored in a measurement report received from the wireless terminal 2 a.As receiving the wireless resource requesting information, the otherwireless base stations 1 b, 1 c send other station information includingthe other station wireless resource information to the connectedwireless base station 1 a in response to the wireless resourcerequesting information. Thus, the scheduler unit 106 of the wirelessbase station 1 a is capable of obtaining the other station wirelessresource information from the other wireless base stations 1 b, 1 c.There are other examples considered as the procedure where the connectedwireless base station 1 a obtains other station wireless resourceinformation from the other wireless base stations 1 b, 1 c, and they aredescribed later (described in a fourth embodiment through a sixthembodiment).

As receiving the other station wireless resource information from theother wireless base stations 1 b, 1 c as described above, the schedulerunit 106 carries out UL scheduling to the subordinate wireless terminal2 a based on the other station wireless resource information.Specifically, the scheduler unit 106 determines the determined wirelessresource, which is the UL wireless resource used for the UL sending fromthe subordinate wireless terminal 2 a, and the determined wireless basestation, which is the other wireless base station 1 b to be the sendingdestination of the UL sending, based on the unused wireless resourcesinformation included in the received other station wireless resourceinformation. Here, it is assumed that the magnitude of the determinedwireless resources is not less than the UL wireless resource amountrequested in the UL schedule requesting information from the wirelessterminal 2 a. The scheduler unit 106 is capable of determining thedetermined wireless resource and the determined wireless base station byan arbitrary criterion based on the unused wireless resources indicatedby the unused wireless resources information. For example, it ispossible that the scheduler unit 106 selects arbitrary one from theunused wireless resources capable of securing the requested UL wirelessresource amount to determine the determined wireless resource therefrom.Then, the scheduler unit 106 is capable of setting the other wirelessbase station 1 b that has sent the selected unused wireless resource(information) as the determined wireless base station.

As described above, the scheduler unit 106 carries out scheduling of theUL wireless resource to the wireless base station 1 b from the wirelessterminal 2 a when the other wireless base station 1 b is selected as theUL sending destination from the wireless terminal 2 a. After that, inorder to generate a DCI, the scheduler unit 106 inputs the UL schedulingresult to the DL control signal generation unit 109. The UL schedulingresult is information including a wireless resource for UL sending (theabove determined wireless resource), an identifier of the wirelessterminals 2 a, a coding and modulation scheme of a signal, and the like.In addition, when selecting the other wireless base station 1 b, thescheduler unit 106 also inputs the UL scheduling result to thetransmission network sending unit 114. Further in this case, thescheduler unit 106 inputs base station identification informationindicating the UL receiving other wireless base station 1 b(corresponding to the determined wireless base station) to thetransmission network sending unit 114.

In contrast, when selecting the local station as the UL sendingdestination from the wireless terminal 2 a, the scheduler unit 106carries out general UL scheduling (the description is omitted). Then, inorder to generate a DCI, the scheduler unit 106 inputs the UL schedulingresult to the DL control signal generation unit 109. For the preparationof UL reception at the local station, the scheduler unit 106 inputs theUL scheduling result to the UL frame analysis unit 102.

Meanwhile, when DL data occurs, the scheduler unit 106 schedules DLsending. In this case, the scheduler unit 106 carries out general DLscheduling (the description is omitted). In order to generate a DCI, thescheduler unit 106 inputs the DL scheduling result to the DL controlsignal generation unit 109. The DL scheduling result is informationincluding a wireless resource for DL sending, an identifier of thewireless terminal 2 a, a coding and modulation scheme of a signal, andthe like. In addition, the scheduler unit 106 inputs DL data to the DLdata signal generation unit 107.

Back to the descriptions in FIG. 5, as the DL data is inputted from thescheduler unit 106, the DL data signal generation unit 107 generates aDL data signal and inputs it to a DL data coding and modulation unit.The DL data coding and modulation unit codes and modulates the DL datasignal based on the coding scheme and the modulation scheme inputtedfrom the scheduler unit 106 and inputs it to the DL frame generationunit 112.

A DL control information generation unit generates DL controlinformation based on the scheduling result inputted from the schedulerunit 106 and inputs it to the DL control signal coding and modulationunit 110. As an example, the DL control signal generation unit 109generates the DCI described before based on the inputted schedulingresult. The DL control signal generation unit 109 sets an RB assignmentvalue of the DCI based on the determined wireless resource included inthe scheduling result inputted from the scheduler unit 106. In addition,the DL control signal generation unit 109 sets the wireless terminalidentifier inputted from the scheduler as an RNTI value and sets themodulation scheme and the coding scheme as an MCS value. The DL controlsignal generation unit 109 inputs the generated DL control signal to theDL control signal coding and modulation unit 110.

The DL control signal coding and modulation unit 110 codes and modulatesthe DL control signal based on the predetermined modulation scheme andcoding scheme and inputs it to the DL frame generation unit 112. The DLreference signal generation unit 111 generates the DL reference signaland inputs it to the DL frame generation unit 112.

The DL frame generation unit 112 places (also called as maps) the DLdata signal, the DL control signal, and the DL reference signal aftercoding and modulation in a DL frame and generates a DL frame. The DLframe generation unit 112 carries out mapping of each DL signal usingthe DL scheduling result inputted from the scheduler unit 106. That is,the DL frame generation unit 112 carries out mapping of each signal tothe wireless resource (RB) defined in the DL scheduling result inputtedfrom the scheduler unit 106. The DL frame generation unit 112 inputs thebaseband signal corresponding to the generated DL frame to the DLwireless sending unit 113.

The DL wireless sending unit 113 upconverts the baseband signalcorresponding to the inputted DL frame to a wireless signal by frequencyconversion and the like and wirelessly sends the wireless signal to thewireless terminal 2 a.

The transmission network sending unit 114 sends a data signal and acontrol signal to the other wireless base stations 1 b, 1 c, othercontrol devices, relay devices, and the like via the backhaul network.As an example, when the scheduler unit 106 selects other than the localstation as the UL sending destination, the transmission network sendingunit 114 sends the wireless resource requesting information describedabove to the other wireless base stations 1 b, 1 c. The sending of thewireless resource requesting information is carried out by accepting aninput of base station identifiers indicating the other wireless basestations 1 b, 1 c from the scheduler unit 106. As an example, when thescheduler unit 106 selects the other wireless base station 1 b as the ULsending destination, the transmission network sending unit 114 sends thedetermined wireless resource information described above to the otherwireless base station 1 b. The sending of the determined wirelessresource information is carried out by accepting an input of the ULscheduling result and the base station identifier from the schedulerunit 106.

The transmission network receiving unit 115 receives a data signal and acontrol signal from the other wireless base stations 1 b, 1 c, othercontrol devices, relay devices, and the like via the backhaul network.For example, when the scheduler unit 106 selects other than the localstation as the UL sending destination, the transmission networkreceiving unit 115 receives the other station wireless resourceinformation described before from the other wireless base stations 1 b,1 c. The transmission network receiving unit 115 inputs the receivedother station wireless resource information to the scheduler unit 106.

Next, descriptions are given to the other wireless base station 1 b inthe first embodiment (the other wireless base station 1 c is similar).

Although the other wireless base station 1 b also has a functionalconfiguration same as FIG. 5, different process is carried out in a partof the functions. It goes without saying that the respective wirelessbase stations 1 may be provided with both a function provided in theconnected wireless base station 1 a and a function provided in the otherwireless base station 1 b. In other words, the respective wireless basestations are capable of behaving as the connected wireless base stationto a certain wireless terminal and behaving as another wireless basestation to another wireless terminal.

The transmission network receiving unit 115 of the other wireless basestation 1 b receives a data signal and a control signal from theconnected wireless base station 1 a, other control devices, relaydevices, and the like connected to the backhaul network. As an example,when the connected wireless base station 1 a selects other than thelocal station (connected wireless base station 1 a) as the UL sendingdestination from the subordinate wireless terminal 2 a, the transmissionnetwork receiving unit 115 receives the wireless resource requestinginformation described before from the connected wireless base station 1a. The transmission network receiving unit 115 inputs the receivedwireless resource requesting information to the scheduler unit 106. Asanother example, the transmission network receiving unit 115 receivesthe determined wireless resource information described before from theconnected wireless base station 1 a. The transmission network receivingunit 115 inputs the received determined wireless resource assignmentinformation to the scheduler unit 106.

The scheduler unit 106 of the other wireless base station 1 b generatesother station wireless resource information based on the inputtedwireless resource requesting information. In the present embodiment, asdescribed before, the other station wireless resource informationincludes the unused wireless resources information, which is informationindicating UL resources not used by the other wireless base station 1 b.The scheduler unit 106 generates the unused wireless resourcesinformation as follows.

The scheduler unit 106 of the other wireless base station 1 bsubjectively and also fully determines scheduling of each wirelessterminal 2 b subordinate to the other wireless base station 1 b.Therefore, the scheduler unit 106 recognizes fixed scheduling (wirelessresource to be used) in the present and future of each subordinatewireless terminal 2 b. In addition, the scheduler unit 106 is alsocapable of controlling not to use a certain wireless resource in thefuture (not to use a certain frequency range in a certain period).Accordingly, the scheduler unit 106 of the other wireless base station 1b is capable of recognizing a wireless resource not used by the localstation (other wireless base station 1 b), in other words, a wirelessresource not to be scheduled for the subordinate wireless terminal 2 bby the local station. With that, the scheduler unit 106 of the otherwireless base station 1 b selects a part or all of the wirelessresources not used by the local station to set information indicatingthe selected wireless resource as the unused wireless resourcesinformation. Then, the scheduler unit 106 generates other stationwireless resource information including the unused wireless resourcesinformation. The scheduler unit 106 inputs the generated other stationwireless resource information to the transmission network sending unit114.

In addition, the scheduler unit 106 of the other wireless base station 1b carries out scheduling to accept the UL sending from the wirelessterminal 2 a subordinate to the connected wireless base station 1 abased on the determined wireless resource information received from theconnected wireless base station 1 a. The determined wireless resourceinformation is determined by the connected wireless base station 1 abased on the unused wireless resources information sent earlier, and isinformation indicating a part or all of the UL wireless resourceindicated by the unused wireless resources information. The schedulerunit 106 inputs the UL scheduling result that reflects the received ULresource assignment information to the UL frame analysis unit 102. TheUL frame analysis unit 102 extracts respective information from the ULframe based on the UL scheduling result. Thus, it becomes possible thatthe other wireless base station 1 b receives data on a UL from thewireless terminal 2 a subordinate to the connected wireless base station1 a.

When the connected wireless base station 1 a selects the other wirelessbase station 1 b as the UL sending destination, the transmission networksending unit 114 of the other wireless base station 1 b in the presentembodiment sends the other station wireless resource informationincluding the unused wireless resources information to the connectedwireless base station 1 a. The sending is carried out by accepting aninput of the other station wireless resource information from thescheduler unit 106.

Next, descriptions are given to the wireless terminal 2 a in the firstembodiment.

FIG. 6 is a diagram illustrating one example of a functionalconfiguration of the wireless terminals 2 a in the first embodiment. Thewireless terminal 2 a is provided with, for example, a DL wirelessreceiving unit 201, a DL frame analysis unit 202, a DL reference signalprocessing unit 203, a DL control signal demodulation and decoding unit204, a DL data signal demodulation and decoding unit 205, an upper layerunit 206, a UL schedule management unit 207, a UL data signal generationunit 208, a UL data signal coding and modulation unit 209, a UL controlsignal generation unit 210, a UL control signal coding and modulationunit 211, a UL reference signal generation unit 212, a UL framegeneration unit 213, and a UL wireless sending unit 214.

The DL wireless receiving unit 201 receives a DL wireless signal,downconverts the received wireless signal by frequency conversion andthe like to convert it to a baseband signal corresponding to the DLframe, and outputs it to the DL frame analysis unit 202. The DL frameanalysis unit 202 extracts a DL data signal, a DL control signal, and aDL reference signal from the baseband signal corresponding to the DLframe. Then, the DL frame analysis unit 202 outputs the DL referencesignal to the DL reference signal processing unit 203, outputs the DLcontrol signal to the DL control signal demodulation and decoding unit204, and outputs the DL data signal to the DL data signal demodulationand decoding unit 205.

The DL reference signal processing unit 203 of the wireless terminal 2 aestimates DL channel characteristics based on the DL reference signaland outputs the DL channel characteristics respectively to the DLcontrol signal demodulation and decoding unit 204 and the DL data signaldemodulation and decoding unit 205.

The DL control signal demodulation and decoding unit 204 demodulates theDL control signal and extracts DL control information by carrying outerror correction and decoding. The DL control signal demodulation anddecoding unit 204 carries out demodulation and decoding of the DLcontrol signal using the DL channel characteristics and predetermineddemodulation scheme and error correction and decoding scheme. Asobtaining the DCI, which is the DL control information, by demodulationand decoding, the DL control signal demodulation and decoding unit 204recognizes (detects) a DCI towards itself based on the RNTI includedtherein. The DL control signal demodulation and decoding unit 204recognizes (detects) whether the scope of DCI application is UL data(PUSCH) or DL data (PDSCH) based on the DCI format. Regarding the DCItowards itself that targets the DL data, the DL control signaldemodulation and decoding unit 204 inputs the RB assignment and the MCSincluded in the DCI to the DL data signal demodulation and decoding unit205. Regarding the DCI towards itself that targets the UL data, the DLcontrol signal demodulation and decoding unit 204 inputs the RBassignment and the MCS included in the DCI to the UL schedule managementunit 207.

The DL data signal demodulation and decoding unit 205 demodulates the DLdata signal and extracts DL data information by carrying out errorcorrection and decoding. In the DL data signal, one or more items ofdata information to the wireless terminal 2 a are multiplexed. The DLdata signal demodulation and decoding unit 205 carries out extraction ofa DL data signal towards itself using the RB assignment inputted fromthe DL control signal demodulation and decoding unit 204. After that,the DL data signal demodulation and decoding unit 205 carries outdemodulation and decoding of the DL data signal based on the DL channelcharacteristics and the MCS inputted from the DL control signaldemodulation and decoding unit 204. The DL data signal demodulation anddecoding unit 205 inputs the obtained DL data to the upper layer unit206.

The upper layer unit 206 processes the inputted DL data to providevarious functions in the wireless terminal 2 a. Although there are, forexample, a voice call, a web browser, a mailer, and the like as thefunctions provided by the upper layer unit 206, there may also be otherarbitrary functions. The upper layer unit 206 generates UL data(information) based on the functions to be provided and inputs them tothe UL schedule management unit 207.

The UL schedule management unit 207 carries out management of the ULschedule when UL data occurs. This is carried out as follows. As UL datais inputted from the upper layer unit 206, the UL schedule managementunit 207 inputs an instruction signal that is to send UL wirelessresource requesting information, which is one of the UL control signal,to the connected wireless base station 1 a to the UL control signalgeneration unit 210 for the purpose of securing the UL wireless resourcein a resource amount to be used for the UL data. With respect to the ULwireless resource requesting information, the connected wireless basestation 1 a notifies the wireless terminal 2 a of the UL wirelessresource by the DCI, which is a DL control signal. After that, asdescribed before, regarding the DCI towards itself that targets the ULdata, the DL control signal demodulation and decoding unit 204 inputsthe RB assignment and the MCS included in the DCI to the UL schedulemanagement unit 207. As they are inputted, the UL schedule managementunit 207 inputs the UL data inputted earlier to the UL data signalgeneration unit 208 for the purpose of carrying out UL data sending.Further, the UL schedule management unit 207 inputs the inputted MCS tothe data signal coding and modulation unit and also inputs the RBassignment to the UL frame generation unit 213.

The UL data signal generation unit 208 generates a UL data signal basedon the inputted UL data information and inputs it to the UL data signalcoding and modulation unit 209. The UL data signal coding and modulationunit 209 makes error correction and coding and modulation of theinputted UL data signal based on the MCS inputted from the UL schedulemanagement unit 207 and inputs it to the UL frame generation unit 213.

The UL control information generation unit generates UL controlinformation based on the instruction signal inputted from the ULschedule management unit 207 and the like and inputs it to the ULcontrol signal coding and modulation unit 211. As examples of the ULcontrol signal, there are UL schedule requesting information to requesta UL wireless resource to the connected wireless base station 1 a whenUL data occurs, a response signal (ACK/NACK signal) to DL data, and thelike. The UL control signal coding and modulation unit 211 makes errorcorrection and coding and modulation of the UL control signal inputtedfrom the UL control signal generation unit 210 based on a predeterminedmodulation scheme and a coding scheme and inputs it to the UL framegeneration unit 213.

The UL reference information generation unit generates UL referenceinformation based on the instruction from the UL schedule managementunit 207 and inputs it to the UL frame generation unit 213. UL referencesignals include, as described before, a DM-RS (demodulation referencesignal) and a SRS (surrounding reference signal).

The UL frame generation unit 213 places (maps) the UL data signal, theUL control signal, and the UL reference signal in a UL frame andgenerates a UL frame. The UL frame generation unit 213 carries outmapping of each signal using the RB assignment inputted from the ULschedule management unit 207. The UL frame generation unit 213 inputs abaseband signal corresponding to the generated UL frame to a wirelesssending unit. The wireless sending unit upconverts the baseband signalcorresponding to the inputted UL frame by frequency conversion and thelike to a wireless signal for wireless sending of the wireless signal tothe wireless base station 1.

Next, based on FIGS. 7 and 8, descriptions are given to a hardwareconfiguration of each device in the wireless communication system of thefirst embodiment.

FIG. 7 illustrates one example of a hardware configuration of thewireless base station 1 in the present embodiment. Each function of thewireless base stations 1 described before are achieved by a part or allof the hardware components below. The wireless base station 1 in anembodiment is provided with a wireless IF (interface) 11, an analogcircuit 12, a digital circuit 13, a processor 14, a memory 15, atransmission network IF 16, and the like.

The wireless IF 11 is an interface device to carry out wirelesscommunication with the wireless terminals 2 and is, for example, anantenna. The analog circuit 12 is a circuit to process an analog signaland may be roughly categorized into those carrying out receivingprocess, those carrying out sending process, and those carrying outother process. The analog circuit that carries out receiving processincludes, for example, a low noise amplifier (LNA), a band pass filter(BPF), a mixer, a low pass filter (LPF), an automatic gain controlamplifier (AGC: automatic gain controller), an analog-to-digitalconverter (ADC), a phase locked loop (PLL), and the like. The analogcircuit that carries out sending process includes, for example, a poweramplifier (PA), a BPF, a mixer, an LPF, a digital-to-analog converter(DAC), a PLL, and the like. The analog circuit that carries out otherprocess includes a duplexer and the like. The digital circuit 13 is acircuit to process a digital signal and includes, for example, an LSI(large scale integration), an FPGA (field-programming gate array), anASIC (application specific integrated circuit), and the like. Theprocessor 14 is a device to process data and includes, for example, aCPU (central processing unit), a DSP (digital signal processor), and thelike. The memory 15 is a device to memorize data and includes, forexample, a ROM (read only memory), a RAM (random access memory), and thelike. The transmission network IF 16 is an interface device to beconnected to the backhaul network of the wireless communication systemby a wired link or a wireless link and to carry out wired communicationor wireless communication with a device on a transmission network sideincluding another wireless base station 1 connected to the backhaulnetwork or the core network.

Descriptions are given to correspondence relationship of the functionalconfiguration and the hardware configuration of the wireless basestation 1.

The UL wireless receiving unit 101 is achieved by, for example, thewireless IF 11 and the analog circuit 12 (those carrying out receivingprocess). That is, the wireless IF 11 receives a UL wireless signal fromthe wireless terminal 2 a, and the analog circuit 12 downconverts thereceived wireless signal by frequency conversion and the like to convertit to a baseband signal corresponding to a UL frame. The UL frameanalysis unit 102 is achieved by, for example, the processor 14, thememory 15, and the digital circuit 13. That is, the processor 14controls the memory 15 as occasion calls, cooperates with the digitalcircuit 13 as occasion calls, and extracts a UL data signal, a ULcontrol signal, and a UL reference signal from the baseband signalcorresponding to the UL frame. In addition, the digital circuit 13 mayalso extract a UL data signal, a UL control signal, and a UL referencesignal from the baseband signal corresponding to the UL frame.

The UL reference signal processing unit 103 is achieved by, for example,the processor 14, the memory 15, and the digital circuit 13. That is,the processor 14 controls the memory 15 as occasion calls, cooperateswith the digital circuit 13 as occasion calls, obtains the UL channelcharacteristics based on the DM-RS, and obtains the UL receiving qualitybased on the SRS. In addition, the digital circuit 13 may also obtainthe UL channel characteristics based on the DM-RS and obtain the ULreceiving quality based on the SRS.

The UL control signal demodulation and decoding unit 104 is achieved by,for example, the processor 14, the memory 15, and the digital circuit13. That is, the processor 14 controls the memory 15 as occasion calls,cooperates with the digital circuit 13 as occasion calls, demodulates aUL control signal, and carries out error correction and decoding. Inaddition, the digital circuit 13 may also demodulate a UL control signaland carry out error correction and decoding. The UL data signaldemodulation and decoding unit 105 is achieved by, for example, theprocessor 14, the memory 15, and the digital circuit 13. That is, theprocessor 14 controls the memory 15 as occasion calls, cooperates withthe digital circuit 13 as occasion calls, demodulates a UL data signal,and carries out error correction and decoding. In addition, the digitalcircuit 13 may also demodulate a UL data signal and carry out errorcorrection and decoding.

The scheduler unit 106 is achieved by, for example, the processor 14,the memory 15, and the digital circuit 13. That is, the processor 14controls the memory 15 as occasion calls, cooperates with the digitalcircuit 13 as occasion calls, and carries out scheduling of the wirelessresource used for wireless communication, and also carries out a varietyof control associated with the scheduling of the wireless resource. Inaddition, the digital circuit 13 may also carry out scheduling of thewireless resource used for wireless communication and also carry out avariety of control associated with the scheduling of the wirelessresource.

The DL data signal generation unit 107 is achieved by, for example, theprocessor 14, the memory 15, and the digital circuit 13. That is, theprocessor 14 controls the memory 15 as occasion calls, cooperates withthe digital circuit 13 as occasion calls, and generates a DL datasignal. In addition, the digital circuit 13 may also generate a DL datasignal. The DL data coding and modulation unit is achieved by, forexample, the processor 14, the memory 15, and the digital circuit 13.That is, the processor 14 controls the memory 15 as occasion calls,cooperates with the digital circuit 13 as occasion calls, and codes andmodulates a DL data signal. In addition, the digital circuit 13 may alsocode and modulate a DL data signal. The DL control informationgeneration unit is achieved by, for example, the processor 14, thememory 15, and the digital circuit 13. That is, the processor 14controls the memory 15 as occasion calls, cooperates with the digitalcircuit 13 as occasion calls, and generates DL control information. Inaddition, the digital circuit 13 may also generate DL controlinformation. The DL data coding and modulation unit is achieved by, forexample, the processor 14, the memory 15, and the digital circuit 13.That is, the processor 14 controls the memory 15 as occasion calls,cooperates with the digital circuit 13 as occasion calls, and codes andmodulates a DL control signal. In addition, the digital circuit 13 mayalso code and modulate a DL control signal. The DL reference signalgeneration unit 111 is achieved by, for example, the processor 14, thememory 15, and the digital circuit 13. That is, the processor 14controls the memory 15 as occasion calls, cooperates with the digitalcircuit 13 as occasion calls, and generates a DL reference signal. Inaddition, the digital circuit 13 may also generate a DL referencesignal. The DL frame generation unit 112 is achieved by, for example,the processor 14, the memory 15, and the digital circuit 13. That is,the processor 14 controls the memory 15 as occasion calls, cooperateswith the digital circuit 13 as occasion calls, places the DL datasignal, the DL control signal, and the DL reference signal after codingand modulation in a DL frame, and generates a DL frame. In addition, thedigital circuit 13 may also place the DL data signal, the DL controlsignal, and the DL reference signal after coding and modulation in a DLframe and generate a DL frame.

The DL wireless sending unit 113 is achieved by, for example, thewireless IF 11 and the analog circuit 12 (those carrying out sendingprocess). That is, the analog circuit 12 upconverts a baseband signalcorresponding to the inputted DL frame by frequency conversion and thelike to a wireless signal, and the wireless IF 11 wirelessly sends thewireless signal to the wireless terminals 2. While the DL wirelesssending unit 113 and the UL wireless receiving unit 101 may be achievedby different wireless IFs 11 (antennas), they may also share onewireless IF 11 by using a duplexer, which is the analog circuit 12.

The transmission network sending unit 114 is achieved by, for example,the transmission network IF 16, the analog circuit 12, the processor 14,the memory 15, and the digital circuit 13. That is, the processor 14controls the memory 15 as occasion calls, cooperates with the digitalcircuit 13 as occasion calls, and converts a data signal and a controlsignal to be sent to a digital baseband signal. In addition, the analogcircuit 12 converts the digital baseband signal to a wired signal or awireless signal, and the transmission network IF 16 sends the wiredsignal or the wireless signal. The transmission network receiving unit115 is achieved by, for example, the transmission network IF 16, theanalog circuit 12, the processor 14, the memory 15, and the digitalcircuit 13. That is, the transmission network IF 16 receives the wiredsignal or the wireless signal, and the analog circuit 12 converts thewired signal or the wireless signal to a digital baseband signal. Inaddition, the processor 14 controls the memory 15 as occasion calls,cooperates with the digital circuit 13 as occasion calls, and converts adigital baseband signal to a data signal and a control signal.

FIG. 8 illustrates one example of a hardware configuration of thewireless terminal 2 in the first embodiment. Each function of thewireless terminals 2 described before is achieved by a part or all ofthe hardware components below. The wireless terminal 2 in the aboveembodiment is provided with a wireless IF 21, an analog circuit 22, adigital circuit 23, a processor 24, a memory 25, an input IF 26, anoutput IF 27, and the like.

The wireless IF 21 is an interface device to carry out wirelesscommunication with the wireless base stations 1 and is, for example, anantenna. The analog circuit 22 is a circuit to process an analog signaland may be roughly categorized into those carrying out receivingprocess, those carrying out sending process, and those carrying outother process. The analog circuit that carries out receiving processincludes, for example, an LNA, a BPF, a mixer, an LPF, an AGC, an ADC, aPLL, and the like. The analog circuit that carries out sending processincludes, for example, a PA, a BPF, a mixer, an LPF, a DAC, a PLL, andthe like. The analog circuit that carries out other process includes aduplexer and the like. The digital circuit 23 includes, for example, anLSI, an FPGA, an ASIC, and the like. The processor 24 is a device toprocess data and includes, for example, a CPU, a DSP, and the like. Thememory 25 is a device to memorize data and includes, for example, a ROM,a RAM, and the like. The input IF 26 is a device to carry out an inputand includes, for example, an operation button, a microphone, and thelike. The output IF 27 is a device to carry out an output and includes,for example, a display, a speaker, and the like.

Descriptions are given to correspondence relationship of the functionalconfiguration and the hardware configuration of the wireless terminal 2.

The DL wireless receiving unit 201 is achieved by, for example, thewireless IF 21 and the analog circuit 22 (those carrying out receivingprocess). That is, the wireless IF 21 receives a DL wireless signal fromthe wireless base station 1, and the analog circuit 22 downconverts thereceived wireless signal by frequency conversion and the like to convertit to a baseband signal corresponding to a DL frame. The DL frameanalysis unit 202 is achieved by, for example, the processor 24, thememory 25, and the digital circuit 23. That is, the processor 24controls the memory 25 as occasion calls, cooperates with the digitalcircuit 23 as occasion calls, and extracts a DL data signal, a DLcontrol signal, and a DL reference signal from the baseband signalcorresponding to the DL frame. In addition, the digital circuit 23 mayalso extract a DL data signal, a DL control signal, and a DL referencesignal from the baseband signal corresponding to the DL frame.

The DL reference signal processing unit 203 is achieved by, for example,the processor 24, the memory 25, and the digital circuit 23. That is,the processor 24 controls the memory 25 as occasion calls, cooperateswith the digital circuit 23 as occasion calls, and obtains the DLchannel characteristics based on the DL reference signal. In addition,the digital circuit 23 may also obtain the DL channel characteristicsbased on the DL reference signal.

The DL control signal demodulation and decoding unit 204 is achieved by,for example, the processor 24, the memory 25, and the digital circuit23. That is, the processor 24 controls the memory 25 as occasion calls,cooperates with the digital circuit 23 as occasion calls, demodulates aDL control signal, and carries out error correction and decoding. Inaddition, the digital circuit 23 may also demodulate a DL control signaland carry out error correction and decoding. The DL data signaldemodulation and decoding unit 205 is achieved by, for example, theprocessor 24, the memory 25, and the digital circuit 23. That is, theprocessor 24 controls the memory 25 as occasion calls, cooperates withthe digital circuit 23 as occasion calls, demodulates a DL data signal,and carries out error correction and decoding. In addition, the digitalcircuit 23 may also demodulate a DL data signal and carry out errorcorrection and decoding.

The upper layer unit 206 is achieved by, for example, the processor 24,the memory 25, and the digital circuit 23. That is, the processor 24controls the memory 25 as occasion calls, cooperates with the digitalcircuit 23 as occasion calls, processes the inputted DL data, providesvarious functions in the wireless terminal 2 a, and also generates ULdata (information) based on the provided functions. In addition, thedigital circuit 23 may also process the inputted DL data, providevarious functions in the wireless terminal 2 a, and also generate ULdata (information) based on the provided functions. The UL schedulemanagement unit 207 is achieved by, for example, the processor 24, thememory 25, and the digital circuit 23. That is, the processor 24controls the memory 25 as occasion calls, cooperates with the digitalcircuit 23 as occasion calls, and carries out management of a ULschedule when UL data occurs. In addition, the digital circuit 23 mayalso carry out management of a UL schedule when UL data occurs.

The UL data signal generation unit 208 is achieved by, for example, theprocessor 24, the memory 25, and the digital circuit 23. That is, theprocessor 24 controls the memory 25 as occasion calls, cooperates withthe digital circuit 23 as occasion calls, and generates a UL datasignal. In addition, the digital circuit 23 may also generate a UL datasignal. The UL data coding and modulation unit is achieved by, forexample, the processor 24, the memory 25, and the digital circuit 23.That is, the processor 24 controls the memory 25 as occasion calls,cooperates with the digital circuit 23 as occasion calls, and codes andmodulates a UL data signal. In addition, the digital circuit 23 may alsocode and modulate a UL data signal. The UL control informationgeneration unit is achieved by, for example, the processor 24, thememory 25, and the digital circuit 23. That is, the processor 24controls the memory 25 as occasion calls, cooperates with the digitalcircuit 23 as occasion calls, and generates UL control information. Inaddition, the digital circuit 23 may also generate UL controlinformation. The UL data coding and modulation unit is achieved by, forexample, the processor 24, the memory 25, and the digital circuit 23.That is, the processor 24 controls the memory 25 as occasion calls,cooperates with the digital circuit 23 as occasion calls, and codes andmodulates a UL control signal. In addition, the digital circuit 23 mayalso code and modulate a UL control signal. The UL reference signalgeneration unit 212 is achieved by, for example, the processor 24, thememory 25, and the digital circuit 23. That is, the processor 24controls the memory 25 as occasion calls, cooperates with the digitalcircuit 23 as occasion calls, and generates a UL reference signal. Inaddition, the digital circuit 23 may also generate a UL referencesignal. The UL frame generation unit 213 is achieved by, for example,the processor 24, the memory 25, and the digital circuit 23. That is,the processor 24 controls the memory 25 as occasion calls, cooperateswith the digital circuit 23 as occasion calls, places the UL datasignal, the UL control signal, and the UL reference signal after codingand modulation in a UL frame, and generates a UL frame. In addition, thedigital circuit 23 may also place the UL data signal, the UL controlsignal, and the UL reference signal after coding and modulation in a ULframe and generate a UL frame.

The UL wireless sending unit 214 is achieved by, for example, thewireless IF 21 and the analog circuit 22 (those carrying out sendingprocess). That is, the analog circuit 22 upconverts a baseband signalcorresponding to the inputted UL frame by frequency conversion and thelike to a wireless signal, and the wireless IF 21 wirelessly sends thewireless signal to the wireless terminals 2. While the UL wirelesssending unit 214 and the DL wireless receiving unit 201 may be achievedby different wireless IFs 21 (antennas), they may also share onewireless IF 21 by using a duplexer, which is the analog circuit 22.

As have been described based on FIGS. 2 through 8, in the wirelesscommunication system in the first embodiment, the connected wirelessbase station 1 a receives other station wireless resource informationincluding unused wireless resources information, which is informationindicating a UL wireless resource not used by the other wireless basestation 1 b from the other wireless base station 1 b. Then, theconnected wireless base station 1 a schedules a UL wireless resourceused for UL sending from the subordinate wireless terminal 2 a to theother wireless base station 1 b based on the received unused wirelessresources information. Thus, it is possible to avoid conflict in a ULwireless resource between UL sending from the wireless terminal 2 asubordinate to the connected wireless base station 1 a to the otherwireless base station 1 b and UL sending from another wireless terminal2 a subordinate to the other wireless base station 1 b to the otherwireless base station 1 b. Accordingly, according to the wirelesscommunication system in the first embodiment, when the wireless terminal2 a carries out communication with different wireless base stations forUL and DL, it is possible that the other wireless base station 1 bdifferent from the connected base station 1 a receives data from thewireless terminal 2 a. In addition, as a result, it is possible toachieve efficient utilization of a wireless resource.

[c] Second Embodiment

In the second embodiment, descriptions are given to an example otherthan the first embodiment when the wireless terminal 2 a carries outcommunication with wireless base stations 1 different for DL and UL. Inthe second embodiment, descriptions are given to a case where sendingdata (DL data) to the subordinate wireless terminal 2 a occurs in thewireless base station 1 a.

In the second embodiment, there are many points in common with the firstembodiment. In the following descriptions, descriptions are given mainlyto the points different from the first embodiment in the secondembodiment.

Based on FIG. 9, descriptions are given to a process sequence in thesecond embodiment. FIG. 9 corresponds to process, as described before,where sending data (DL data) to the subordinate wireless terminal 2 aoccurs in the wireless base station 1 a.

In S201 in FIG. 9, firstly, DL data occurs in the connected wirelessbase station 1 a. For example, DL data occurs when an audio signal,data, and the like are sent from the other wireless terminal 2 b to thesubordinate wireless terminal 2 a, a server on the Internet sends datato the wireless terminal 2 a, and the like.

In S202, as DL data occurs, the connected wireless base station 1 aschedules a DL wireless resource to send the DL data to the wirelessterminal 2 a. Here, the scheduling of a DL wireless resource may use ageneral technique, so that the descriptions are omitted here.

Next, the connected wireless base station 1 a schedules a UL wirelessresource to receive a response signal (ACK/NACK signal) from thewireless terminal 2 a that have received the DL data. This is carriedout as below. The connected wireless base station 1 a obtains the ULreceiving quality from the wireless terminal 2 a and determines whetheror not to set a reception destination of the response signal as thelocal station based on the UL receiving quality in S203. In S204, asdetermining the base station to receive the UL data as any of thewireless base stations 1 other than the local station, the connectedwireless base station 1 a sends wireless resource requesting informationto the other wireless base stations 1 b, 1 c via the transmissionnetwork. In contrast, the other wireless base stations 1 b, 1 crespectively obtain unused wireless resources in S205, and send otherstation wireless resource information including the unused wirelessresources information to the connected wireless base station 1 a via thetransmission network in S206. Then, it is assumed that, in S207, theconnected wireless base station 1 a determines a UL wireless resourcefor the response signal and the other wireless base station 1 b to bethe UL sending destination. S203 through S207 are similar to S103through S107, so that the details are omitted.

In S208 in FIG. 9, next, the connected wireless base station 1 a sendsdetermined wireless resource information, which is informationindicating the selected UL wireless resource, to the subordinatewireless terminal 2 a on a DL wireless signal. At this time, theconnected wireless base station 1 a in the second embodiment sends, inaddition to the determined wireless resource information, DL data on aDL wireless signal as well.

Here, once leaving from FIG. 9, which is a process sequence of thesecond embodiment, descriptions are given to process when the connectedwireless base station 1 a sends DL data in a conventional LTE system. Asscheduling a DL wireless resource to be assigned to DL data, theconnected wireless base station 1 a places (maps) the DL data in the DLwireless resource (resource block) on the DL frame. Together with this,the connected wireless base station 1 a places a DCI (refer to FIG. 4),which is DL control information, in a predetermined region of the DLframe same as the DL data. As illustrated in FIG. 4, the DCI includes RBassignment, which is information indicating the DL wireless resourceassigned to the DL data. Then, the connected wireless base station 1 asends a DL wireless signal including the DL frame to the wirelessterminal 2 a.

The descriptions for the conventional LTE system are continued. Thewireless terminal 2 a receives a DL wireless signal including the DLframe. The wireless terminal 2 a recognizes (detects) the presence of DLdata towards itself based on the RNTI included in the DCI in the DLframe, and recognizes (detects) that the scope of DCI application is theDL data (PDSCH) based on the DCI format. Further, the wireless terminal2 a extracts the DL data based on the RB assignment included in the DCIand carries out demodulation and decoding of the DL data based on theMCS included in the DCI. The wireless terminal 2 a sends a responsesignal (an ACK signal indicating decoding success or a NACK signalindicating decoding failure) to the connected wireless base station 1 aon a UL frame in accordance with the decoding result.

At this time, the wireless terminal 2 a places the response signal inthe UL frame corresponding to the placement of the DCI itself in the DLframe received earlier (note that it is not the placement indicated bythe RB assignment in the DCI). Thus, the connected wireless base station1 a is capable of easily linking the sent DL data with the receivedresponse signal.

Specifically, the following specifications are defined in the LTE.Resource specification in the PUCCH (logical channel for a UL controlsignal) is carried out by a CCE (control channel element) number of thePDCCH (logical channel for a DL control signal) represented by a formula(1). In other words, specification of the UL wireless resource forACK/NACK is carried out by placement of the DCI resource represented bya formula (1).

[Math 1]

n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾  (1)

Here, P₀ is an antenna port, n_(CCE) is a minimum CCE number used forsending of the corresponding DCI (for example, minimum CCE number uponconfiguring the PDCCH), and N_(PUCCH) ⁽¹⁾ is a parameter notified by anupper layer. Although a CCE is a wireless resource unit that a RB isdivided further, details are omitted.

Accordingly, in the conventional LTE system, the DL control information(DCI) related to the DL data and the UL control information (ACK/NACK)are only capable of using a mutually corresponding wireless resource.Accordingly, regarding control information related to the DL data, whenthe other wireless base station 1 b uses a certain UL wireless resourceR1, for example, the connected wireless base station 1 a is not onlyincapable of using the UL wireless resource R1 (to avoid resourceconflict) but also incapable of using a DL wireless resource R1. Even ina situation where the DL resources do not interfere with each other, theconnected wireless base station 1 a in this example has no option but touse a UL wireless resource R2 (≠R1) and a DL wireless resource R2.Accordingly, in the conventional LTE system, scheduling for controlinformation related to the DL data may be considered to be poor inflexibility.

With that, in the present embodiment, it is made possible to separatethe correspondence relationship of the DL control information (DCI)related to DL data and the UL control information (ACK/NACK) and toallow assignment of a wireless resource that does not correspondmutually. Therefore, in the DCI, which is the DL control information, aregion to store an offset in the placement (mapping) from thecorresponding UL control information (referred to as a resource offset)is provided. Then, the wireless terminal 2 a having received the DL dataas well as the DCI places a response signal to the DL data in a wirelessresource that is shifted by the resource offset stored in the DCI fromthe corresponding wireless resource of the DCI.

FIG. 10 illustrates one example of a DCI format according to the secondembodiment. The DCI format in FIG. 10 includes the resource offset. Theresource specification using the resource offset may be represented as aformula (2).

[Math 2]

n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾ +n_(PUCCH) _(_) _(offset)  (1)

Here, n_(PUCCH) _(_) _(offset) is a resource offset of the PUCCH, andthe unit is a CCE.

In such a manner, in the wireless communication system in the secondembodiment, it is possible to assign a non-corresponding wirelessresource to the DL control information (DCI) related to the DL data andthe UL control information (ACK/NACK). For example, when the otherwireless base station 1 b uses a certain UL wireless resource R1 and aDL wireless resource R1, the connected wireless base station 1 a iscapable of using a UL wireless resource R2 (=R1+resource offset) and theDL wireless resource R1. Accordingly, in the wireless communicationsystem in the present embodiment, it becomes possible to carry outflexible scheduling for the control information related to the DL data.

Back to the descriptions of FIG. 9, in S208, the connected wireless basestation 1 a sends the DCI, which is DL control information, and the DLframe including the DL data to the wireless terminal 2 a. The DCIincludes, in addition to the resource offset described before, the RNTI,the RB assignment related to the DL data, the MCS, and the like. Here,this resource offset corresponds to the determined wireless resourceinformation (UL wireless resource for UL sending from the wirelessterminal 2 a to other wireless base station 1 b).

In contrast, in S208, the wireless terminal 2 a receives the DL framesent by the connected wireless base station 1 a. The wireless terminal 2a recognizes (detects) the presence of the DL data towards itself basedon the RNTI included in the DCI in the DL frame, and recognizes(detects) that the scope of DCI application is the DL data (PDSCH) basedon the DCI format. Further, the wireless terminal 2 a extracts DL databased on RB assignment included in the DCI, and carries out demodulationand decoding of the DL data based on the MCS included in the DCI. Thus,in S209, the reception of DL data is completed. The resource offsetincluded in the DCI is to be used when sending a UL control signal(ACK/NACK) and is not used here.

In S210 in FIG. 9, the connected wireless base station 1 a sendsdetermined wireless resource information to the other wireless basestation 1 b, which is a sending source of the unused wireless resourceto be the origin of the determined wireless resource via thetransmission network. Here, the determined wireless resource informationsent by the connected wireless base station 1 a corresponds toinformation indicating placement of adding the resource offset includedin the DCI to the placement of the DCI included in the DL frame sent bythe connected wireless base station 1 a. S208 and S210 may besimultaneous or in the reverse order.

This completes the scheduling of the UL wireless resource to thewireless terminal 2 a by the connected wireless base station 1 a. InS203, when the connected wireless base station 1 a determines the localstation as the base station to receive UL data, regular UL wirelessresource scheduling may be carried out (details are omitted).

In S211 in FIG. 9, in response to the decoding result of S208, thewireless terminal 2 a sends a UL wireless signal including the UL framewhere a response signal (ACK signal indicating decoding success or NACKsignal indicating decoding failure), which is a UL control signal, isplaced. At this time, the wireless terminal 2 a of the presentembodiment places a response signal in a UL frame using the resourceoffset included in the DCI as described before. Specifically, thewireless terminal 2 a has placement of the response signal in the ULframe as placement where the resource offset included in the DCI isadded to the placement of the DCI itself in the DL frame receivedearlier.

In contrast, in S211, the other wireless base station 1 b receives aresponse signal, which is a UL control signal placed in the UL frameincluded in the UL wireless signal sent by the wireless terminal 2 a. Atthis time, in S210, the other wireless base station 1 b receives aresponse signal using the UL wireless resource indicated by thedetermined wireless resource information received from the connectedwireless base station 1 a. As described before, the determined wirelessresource information received from the connected wireless base station 1a is the information indicating placement where the resource offsetincluded in the DCI is added to the placement of the DCI included in theDL frame sent by the connected wireless base station 1 a.

Lastly, in S212, the other wireless base station 1 b sends (transfers)the response signal included in the received UL wireless signal to theconnected wireless base station 1 a via the transmission network. Thiscompletes the reception of a response signal (ACK/NACK) in the connectedwireless base station 1 a in S213.

As described above based on FIGS. 9 and 10, in the wirelesscommunication system of the second embodiment, correspondencerelationship related to the placement of the DL control information(DCI) related to the DL data and the UL control information (ACK/NACK)is separated and sends the information related to the placement of thecorresponding UL control information in the DL control information.Thus, the wireless communication system in the second embodimentexhibits, in addition to the effect obtained in the wirelesscommunication system in the first embodiment, an effect of allowingflexible scheduling to the control information related to the DL data.

The functional configuration and the hardware configuration of therespective device in the second embodiment follow those in the firstembodiment, so that the description is omitted.

[d] Third Embodiment

The third embodiment is a modification that is applicable to the firstembodiment or the second embodiment, and the connected wireless basestation 1 a selects the other wireless base station 1 b, which is a ULsending destination, based on the UL receiving quality notified inadvance from the other wireless base stations 1 b.

In the following descriptions, descriptions are given to a modificationwhere the third embodiment is applied to the first embodiment. Sincethis modification has many points in common with the first embodiment,descriptions are given mainly to the points different from the firstembodiment in the following descriptions. As described before, althoughthe third embodiment may be modified by applying to the secondembodiment, it may be applied similarly to that to the first embodimentand the details are omitted.

Based on FIG. 11, descriptions are given to a process sequence of amodification where the third embodiment is applied to the firstembodiment. Since S301 through S303 in FIG. 11 are similar to S101through S103 in FIG. 3, the description is omitted. In S304, theconnected wireless base station 1 a sends, in addition to wirelessresource requesting information (similar to S104 in FIG. 3), SRSresource information to the other wireless base stations 1 b, 1 c. Here,the SRS resource information indicates resource information to be usedfor reception of an SRS, which is a UL reference signal for UL receivingquality measurement generated by the wireless terminal 2 a. The SRSresource information includes, for example, an RB to which an SRS isassigned, data series information of an SRS, and the like. Since thegenerated SRS is different for each wireless terminal 2, only theconnected wireless base station 1 a that regularly recognizes the SRSresource information is capable of receiving it. By obtaining the SRSresource information, the other wireless base stations 1 b, 1 c becomecapable of receiving an SRS.

In S305 in FIG. 11, the other wireless base stations 1 b, 1 c confirm aused wireless resource (similar to S105 in FIG. 3). Next, in S306, theother wireless base stations 1 b, 1 c receive an SRS from the wirelessterminal 2 a using the SRS resource information and measures the ULreceiving quality. Then, in S307, the other wireless base stations 1 b,1 c send, in addition to the other station wireless resource information(similar to S106 in FIG. 3), the UL receiving quality informationmeasured in S306 to the connected wireless base station 1 a.

In S308 in FIG. 11, the connected wireless base station 1 a is capableof using the received UL receiving quality information in thedetermination of UL reception destination and UL resource. As anexample, the connected wireless base station 1 a is capable ofdetermining, among the other wireless base stations 1 b, 1 c capable ofsecuring the UL wireless resource in the amount requested in the ULschedule requesting information (this is obtained by the other stationwireless resource information), that having best receiving qualityindicated by the received UL receiving quality information as the ULreception destination. Since S309 through S313 in FIG. 11 are similar toS108 through S112 in FIG. 3, the description is omitted.

As descriptions are given above based on FIG. 11, in the wirelesscommunication system of the third embodiment, the connected wirelessbase station 1 a selects the other wireless base station 1 b, which isthe UL sending destination, based on the UL receiving quality notifiedin advance from the other wireless base stations 1 b, 1 c. In addition,therefore, the connected wireless base station 1 a sends the SRSresource information to the other wireless base stations 1 b, 1 c inadvance. Thus, the wireless communication system in the third embodimentexhibits, in addition to an effect obtained by the wirelesscommunication system in the first embodiment, an effect of allowingselection of the other wireless base stations 1 b, 1 c having good ULreceiving quality as the UL sending destination.

The functional configuration and the hardware configuration of therespective device in the third embodiment follow those in the firstembodiment, so that the description is omitted.

[e] Fourth Embodiment

The fourth embodiment is a modification that is applicable to as any ofthe first embodiment through the third embodiment, and the connectedwireless base station 1 a notifies the other wireless base stations 1 b,1 c in advance of a wireless resource amount to be used for the ULsending of the wireless terminal 2 a.

In the following descriptions, descriptions are given to a modificationwhere the fourth embodiment is applied to the first embodiment. Sincethis modification has many points in common with the first embodiment,descriptions are given mainly to the points different from the firstembodiment in the following descriptions. As described before, althoughthe fourth embodiment may be modified by applying to the secondembodiment or the third embodiment, it may be applied similarly to thatto the first embodiment and the details are omitted.

Based on FIG. 12, descriptions are given to a process sequence of amodification where the fourth embodiment is applied to the firstembodiment.

Since S401 through S403 in FIG. 12 are similar to S101 through S103 inFIG. 3, the description is omitted. In S404 in FIG. 12, the connectedwireless base station 1 a sends wireless resource requestinginformation, which is information to request a UL wireless resource, tothe other wireless base stations 1 b, 1 c via the transmission network.At this time, the connected wireless base station 1 a in the presentembodiment stores requested amount information of the UL wirelessresource included in the UL schedule requesting information received inS402 in the wireless resource requesting information for sending.

In S405 in FIG. 12, as receiving wireless resource requestinginformation respectively, the other wireless base stations 1 b, 1 cobtain unused wireless resources. At this time, the other wireless basestations 1 b, 1 c in the present embodiment obtain the unused wirelessresources of the requested amount based on the UL wireless resourceamount information included in the received wireless resource requestinginformation. In S406, the other wireless base stations 1 b, 1 c sendother station wireless resource information including unused wirelessresources information indicating the obtained unused wireless resourcesto the connected wireless base station 1 a via the transmission network,respectively. The other station wireless resource information sent inS406 satisfies the requested amount (of the UL wireless resource)included in the wireless resource requesting information received inS404.

In S406, the connected wireless base station 1 a receives other stationwireless resource information including the unused wireless resourcesinformation respectively from the other wireless base stations 1 b, 1 c.Then, in S407, the connected wireless base station 1 a selects the ULwireless resource that is used for UL data sending from the wirelessterminal 2 a based on the received unused wireless resourcesinformation. Here, the connected wireless base station 1 a in the firstembodiment arbitrarily selects unused wireless resources of therequested wireless resource amount based on the received unused wirelessresources information in S107 in FIG. 3. In contrast, the unusedwireless resources information received by the connected wireless basestation 1 a of the present embodiment indicates unused wirelessresources of the requested wireless resource amount. Therefore, theconnected wireless base station 1 a in the present embodiment may selectone item of the unused wireless resources information receivedrespectively from the other wireless base stations 1 b, 1 c in S407.That is, in the connected wireless base station 1 a of the presentembodiment, selection of the UL wireless resource based on the unusedwireless resources and selection of the other wireless base station 1 bto be a sending destination of UL sending are equivalent. Here, it isassumed that the connected wireless base station 1 a selects the unusedwireless resources of the other wireless base station 1 b as the ULwireless resource.

In S408 in FIG. 12, the connected wireless base station 1 a sends thedetermined wireless resource information to the wireless terminal 2 a(similar to S108 in FIG. 3). In S409, the connected wireless basestation 1 a sends response information indicating to be selected as theother wireless base station 1 b to be a sending destination of ULsending to the other wireless base station 1 b to be the sendingdestination of the UL sending. Here, the connected wireless base station1 a in the present embodiment, different from the connected wirelessbase station 1 a in the first embodiment, does not have to notify theother wireless base station 1 b of information indicating the selectedunused wireless resources. This is because the other wireless basestation 1 b recognizes the selected unused wireless resources. SinceS410 through S412 in FIG. 12 are same as S110 through S112 in FIG. 3,the description is omitted.

In the fourth embodiment, compared with the first embodiment, although asize of wireless resource requesting information is slightly greater forincluding the UL wireless resource amount information, the other stationwireless resource information (unused wireless resources information)may be same or smaller. In addition, the connected wireless base station1 a may send, instead of the determined wireless resource information,the response information. Accordingly, according to the fourthembodiment, compared with the first embodiment, an effect of suppressingthe information amount sent and received between the wireless basestations 1 is expected.

The functional configuration and the hardware configuration of therespective device in the fourth embodiment follow those in the firstembodiment, so that the description is omitted.

[f] Fifth Embodiment

The fifth embodiment is a modification that is applicable to any of thefirst embodiment through the third embodiment, and the connectedwireless base station 1 a notifies of, without obtaining other stationwireless resource information from the other wireless base stations 1 b,1 c, a UL wireless resource used for the UL sending from the wirelessterminal 2 a. In other words, the connected wireless base station 1 anotifies the other wireless base stations 1 b, 1 a one-sidedly of the ULwireless resource used for the UL sending from the wireless terminal 2a.

In the following descriptions, descriptions are given to a modificationwhere the fifth embodiment is applied to the first embodiment. Sincethis modification has many points in common with the first embodiment,descriptions are given mainly to the points different from the firstembodiment in the following descriptions. As described before, althoughthe fifth embodiment may be modified by applying to the secondembodiment or the third embodiment, it may be applied similarly to thatto the first embodiment and the details are omitted.

Based on FIG. 13, descriptions are given to a process sequence of amodification where the fifth embodiment is applied to the firstembodiment.

Since S501 through S503 in FIG. 13 is similar to S101 through S103 inFIG. 3, the description is omitted. When the UL reception destination isdetermined as other than the local station in S503, the connectedwireless base station 1 a further determines a UL wireless resource anda UL reception destination used for the UL reception in S504. Theconnected wireless base station 1 a is capable of determining the ULwireless resource and the UL reception destination used for the ULreception in an arbitrary method.

In S505, the connected wireless base station 1 a sends the determined ULwireless resource to the wireless terminal 2 a (similar to S108 in FIG.3). Then, in S506, the connected wireless base station 1 a sendswireless resource requesting information, which is the information torequest the determined UL wireless resource, to the other wireless basestation 1 b, which is the determined UL sending destination, via thetransmission network. Since S507 through S509 in FIG. 13 are similar toS110 through S112 in FIG. 3, the description is omitted.

In the fifth embodiment, compared with the first embodiment, the otherstation wireless resource information (unused wireless resourcesinformation) becomes not requested and the information sent from theconnected wireless base station 1 a to the other wireless base station 1b is also reduced. Accordingly, according to the fifth embodiment,compared with the first embodiment, an effect of suppressing theinformation amount sent and received between the wireless base stations1 is expected.

The functional configuration and the hardware configuration of therespective device in the fifth embodiment follow those in the firstembodiment, so that the description is omitted.

[g] Sixth Embodiment

The sixth embodiment is a modification that is applicable to as any ofthe first embodiment through the third embodiment, and the otherwireless base stations 1 b, 1 c sense an event to be an opportunity,thereby sending other station wireless resource information to theconnected wireless base station 1 a. In other words, without sendingwireless resource requesting information from the connected wirelessbase station 1 a to the other station wireless base stations 1 b, 1 c,the other station wireless base stations 1 b, 1 c send other stationwireless resource information to the connected wireless base station 1a.

In the following descriptions, descriptions are given to a modificationwhere the sixth embodiment is applied to the first embodiment. Sincethis modification has many points in common with the first embodiment,descriptions are given mainly to the points different from the firstembodiment in the following descriptions. As described before, althoughthe sixth embodiment may be modified by applying to the secondembodiment or the third embodiment, it may be applied similarly to thatto the first embodiment and the details are omitted.

Based on FIG. 14, descriptions are given to a process sequence of amodification where the sixth embodiment is applied to the firstembodiment.

In S601 in FIG. 14, the other wireless base stations 1 b, 1 c sense apredetermined event to be a trigger (opportunity) to send other stationwireless resource information. This event may be an arbitrary event andmay be, as an example, a lapse of predetermined time from the lastsending of the other station wireless resource information. As anotherexample, it may be the UL wireless used resource amount in the otherwireless base stations 1 b, 1 c at a predetermined value or less. Then,in S602 and S603, the other station wireless base stations 1 b, 1 cconfirm the used wireless resource and send the other station wirelessresource information (similar to S105 and S106 in FIG. 3).

In addition, in S604 through S606 in FIG. 14, UL data occurs in thewireless terminal 2 a, and the wireless terminal 2 a sends UL schedulerequesting information and the connected wireless base station 1 adetermines whether or not to set the UL reception destination as thelocal station (similar to S101 through S103 in FIG. 3). Then, when theUL reception destination is determined as other than the local stationin S606, the connected wireless base station 1 a determines, in S607, aUL wireless resource and a UL reception destination based on the otherstation wireless resource information received in S603. Since S607through S612 in FIG. 14 are similar to S107 through S112 in FIG. 3, thedescription is omitted. Although S601 through S603 in FIG. 14 arecarried out at a timing before S605, they do not have to be so and S601through S603 may be at any timing as long as before S607.

In the sixth embodiment, compared with the first embodiment, thewireless resource requesting information becomes not requested.Accordingly, according to the sixth embodiment, compared with the firstembodiment, an effect of suppressing information amount sent andreceived between the wireless base stations 1 is expected.

The functional configuration and the hardware configuration of therespective device in the sixth embodiment follow those in the firstembodiment, so that the description is omitted.

[h] Seventh Embodiment

In the seventh embodiment, the wireless terminal 2 a generates and sendsa DM-RS, which is one of the UL reference signals, in accordance withthe other wireless base station 1 b, which is a UL sending destination.It is possible to combine the seventh embodiment with the firstembodiment or the second embodiment, and there are many points in commonwith them. In the following descriptions, descriptions are given mainlyto the points in the seventh embodiment different from the firstembodiment in the following descriptions.

In a conventional LTE system and the wireless communication system ofthe first embodiment, when sending a UL wireless frame, the wirelessterminal 2 a generates a DM-RS, which is one of the UL reference signal,and maps it in a UL wireless frame for sending. The connected wirelessbase station 1 a that has received the UL wireless frame demodulates theUL control signal and the data signal using channel characteristics toestimate the channel characteristics based on the DM-RS.

Here, the DM-RS is information (pattern) different for each wirelessbase station 1. Specifically, the DM-RS is generated based on a basestation identifier. In a regular LTE system, the wireless terminal 2 agenerates a DM-RS for the connected wireless base station 1 a using theidentifier of the connected wireless base station 1 a and sends it in aUL wireless frame. Then, the connected wireless base station 1 a carriesout channel estimation by analyzing the DM-RS in the received ULwireless frame using the identifier of the connected wireless basestation 1 a. Thus, the connected wireless base station 1 a is capable ofappropriately receiving the DM-RS and capable of estimating the channelcharacteristics with high precision, so that decoding errors aresuppressed.

However, a problem occurs in the first embodiment and the secondembodiment when the UL sending destination of the wireless terminal 2 abecomes the other wireless base station 1 b. Even when the wirelessterminal 2 a sends the DM-RS towards the connected wireless base station1 a, the other wireless base station 1 b receives the DM-RS and utilizesit for demodulation. Since the DM-RS towards the other wireless basestation 1 b is generally different from the DM-RS towards the connectedwireless base station 1 a, the other wireless base station 1 b is notcapable of appropriately estimating the channel characteristics based onthe DM-RS. In this case, it turns out to increase decoding errors andthus not preferred.

In order to solve this problem, in the seventh embodiment, when the ULsending destination of the subordinate wireless terminal 2 a is theother wireless base station 1 b, the connected wireless base station 1 astores an identifier of the other wireless base station 1 b in the DLcontrol information (DCI) for sending. Then, the wireless terminal 2 ahaving received the DL wireless frame, when sending the UL wirelessframe, generates the DM-RS using the identifier of the other wirelessbase station 1 b and maps the DM-RS in the UL wireless frame forsending.

FIG. 15 illustrates a DCI format in the seventh embodiment. FIG. 15 (A)is a DCI format of a modification where the seventh embodiment isapplied to the first embodiment. FIG. 15 (B) is a DCI format of amodification where the seventh embodiment is applied to the secondembodiment. The DCI formats in FIG. 15 both have a region to store a ULsending destination identifier, which is an identifier of the otherwireless base station 1 b.

According to the seventh embodiment, the wireless terminal 2 a iscapable of generating and sending the DM-RS towards the other wirelessbase station 1 b, so that an effect of suppressing decoding errors inthe other wireless base station 1 b is obtained.

The functional configuration and the hardware configuration of therespective device in the seventh embodiment follow those in the firstembodiment, so that the description is omitted.

[i] Eighth Embodiment

The eighth embodiment is also to solve the problem same as the seventhembodiment, and it is possible to combine with the first embodiment orthe second embodiment. Since the eighth embodiment has many points incommon with the seventh embodiment, descriptions are given mainly to thepoints in the eighth embodiment different from the seventh embodiment inthe following descriptions.

In the eighth embodiment, it does not have to store an identifier of theother wireless base station 1 b in the DCI as in the seventh embodiment.Instead, in the eighth embodiment, the other wireless base station 1 banalyzes the DM-RS in the received UL wireless frame using theidentifier of the connected wireless base station 1 a (not theidentifier of itself) and carries out channel estimation. The otherwireless base station 1 b is capable of learning the identifier of theconnected wireless base station 1 a in a message sent and received withthe connected wireless base station 1 a.

According to the eighth embodiment, the other wireless base station 1 bis capable of appropriately receiving the DM-RS towards the connectedwireless base station 1 a and capable of estimating the channelcharacteristics with high precision, so that an effect of suppressingdecoding errors is obtained. Comparing the seventh embodiment with theeighth embodiment, the former has to use a function compatible with boththe wireless base stations 1 and the wireless terminals 2, while thelatter has to use a function compatible only with the wireless basestations 1, so that the latter is considered to be easier forintroduction.

The functional configuration and the hardware configuration of therespective device in the eighth embodiment follow those in the firstembodiment, so that the description is omitted.

[j] Ninth Embodiment

The ninth embodiment is also to solve the problem same as the seventhembodiment and the eighth embodiment, and it is possible to combine withthe first embodiment or the second embodiment. The ninth embodiment isequivalent to an embodiment in which the seventh embodiment and theeighth embodiment are combined.

When an identifier of the other wireless base station 1 b is stored inthe DCI in the received DL wireless frame, the wireless terminal 2 a inthe present embodiment generates the DM-RS using the identifier of theother wireless base station 1 b. At this time, the other wireless basestation 1 b analyzes the DM-RS in the UL wireless frame received asregularly using the identifier of itself and carries out channelestimation.

In contrast, when the identifier of the other wireless base station 1 bis not stored in the DCI, the wireless terminal 2 a generates the DM-RSusing an identifier of the connected wireless base station 1 a. At thistime, the other wireless base station 1 b analyzes the DM-RS in thereceived UL wireless frame using the identifier of the connectedwireless terminal 2 a and carries out channel estimation.

The other wireless base station 1 b is regularly not capable of learningwhether or not an identifier of the other wireless base station 1 b isstored in the DCI. Therefore, the other wireless base station 1 b has tobe notified of whether or not the identifier of the other wireless basestation 1 b is stored in the DCI from the connected wireless basestation 1 a in advance.

By the ninth embodiment as well, similar to the seventh and eighthembodiments, an effect of suppressing decoding errors in the otherwireless base station 1 b is obtained.

The functional configuration and the hardware configuration of therespective device in the ninth embodiment follow those in the firstembodiment, so that the description is omitted.

[k] Other Embodiments

In the first through ninth embodiments described above, when thewireless terminal 2 a is UL sent to the other wireless base station 1 b,the connected wireless base station 1 a carries out determination of theother wireless base station 1 b to be the destination (determinedwireless base station) and the UL wireless resource to be used(determined wireless resource). However, the subject of suchdetermination is not limited to the connected wireless base station 1 a.

For example, an upper station (upper device) connected to the corenetwork and the like may also determine the determined wireless basestation and the determined wireless resource. In addition, the otherwireless base station 1 b different from the connected wireless basestation 1 a may also determine the determined wireless base station andthe determined wireless resource. Further, the wireless terminal 2 a mayalso determine the determined wireless base station and the determinedwireless resource.

Further, an upper station (upper device), the other wireless basestation 1 b, the wireless terminal 2 a, and the like may also receiveother station wireless resource information from the other wireless basestations 1 b, 1 c in a procedure similar to that carried out by theconnected wireless base station 1 a in the first through ninthembodiments described above. Then, the upper station (upper device), theother wireless base station 1 b, wireless terminal 2 a, and the like mayalso determine the determined wireless base station and the determinedwireless resource based on the received other station wireless resourceinformation.

By the way, in this application, for example, “connected to” is able tobe replaced with “coupled to”. Moreover, for example, when an element isreferred to as being “connected to” or “coupled to” another element, itcan be not only directly but also indirectly connected or coupled to theother element (namely, intervening elements may be present). So do“connecting to”, “coupling to”, “connection to”, “coupling to” and soon.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinvention have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A wireless base station, comprising: a wirelesstransceiver configured to transmit to a wireless terminal a downlinkframe including a downlink control information, the wireless downlinkcontrol information includes information representing a specifiedoffset, wherein the wireless transceiver is further configured toreceive an uplink frame from the wireless terminal; and a processorcircuit coupled to the wireless transceiver and configured to determineuplink control information from the uplink frame, the uplink controlinformation being offset by at least the specified offset from alocation in the uplink frame that is the same as a location where thedownlink control information was located in the downlink frame.
 2. Thebase station of claim 1, wherein the offset is specified in a hybridautomatic repeat request-acknowledgment (HARQ-ACK) resource offset fieldof a Long Term Evolution (LTE) downlink control information (DCI)assignment.
 3. The base station of claim 1, wherein the downlink controlinformation is Downlink Control Information (DCI) of Long Term Evolution(LTE).
 4. The base station of claim 1, wherein the downlink frame andthe uplink frame are subframes of Long Term Evolution (LTE).
 5. The basestation of claim 1, wherein the uplink control information acknowledgesa status of decoding of data specified to be sent by the base station asindicated in the wireless downlink control information.
 6. The basestation of claim 1, wherein the uplink control information is mapped toa first uplink control resource element of uplink control resourceelements that are resource units used for transmissions of uplinkcontrol signals in the uplink frame.
 7. The base station of claim 1,wherein the processor circuit is further configured to: determine thelocation of the uplink control information from the uplink frame basedon the location of the downlink control information in the transmitteddownlink frame and the specified offset.
 8. The base station of claim 1,wherein the processor circuit is further configured to: determine thelocation of the uplink control information from the uplink frame basedon the location of the downlink control information in the transmitteddownlink frame, the specified offset, and a parameter supplied by anupper layer.
 9. The base station of claim 1, wherein the processorcircuit is further configured to: utilize the uplink control informationfor an acknowledgement of the status of decoding of data sent to thewireless terminal.
 10. The base station of claim 1, wherein the uplinkcontrol information is mapped to a first uplink control resource elementof at least one uplink control resource elements in the uplink frame,wherein the first uplink control resource element location is determinedby shifting, with respect to a second uplink control resource elementlocation of the uplink control resource elements, by at least the offsetwhich is expressed in units of uplink control resource elements, thesecond uplink control resource element location in the uplink framecorresponding to the location where the downlink control information waslocated in the downlink frame.
 11. The base station of claim 1, whereinthe downlink control information is in the form of downlink controlResource Elements (RE) that make up Control Channel Elements (CCEs) ofLTE wireless communication standard.
 12. The base station of claim 1,wherein the uplink control information location for the wirelessterminal n_(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ is given by:n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾, wheren_(CCE) is a minimum number of LTE control channel elements (CCE) usedfor sending of the corresponding resource allocation control signal;n_(PUCCH) _(_) _(offset) is the specified offset expressed in CCE units;and P₀ is an antenna port.
 13. The base station of claim 1, wherein theuplink control information location for the wireless terminal n_(PUCCH)^((1,{tilde over (p)}) ⁰ ⁾ is given by:n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾ +n_(PUCCH) _(_) _(offset), where n_(CCE) is a minimum number of LTEcontrol channel elements (CCE) used for sending of the correspondingresource allocation control signal; n_(PUCCH) _(_) _(offset) is thespecified offset expressed in CCE units; P₀ is an antenna port; andN_(PUCCH) ⁽¹⁾ is a parameter specified by an upper layer.
 14. A methodfor use in a wireless terminal, comprising: determining, from a locationwithin a downlink frame received by the wireless terminal, wirelessterminal downlink control information for the wireless terminal, thewireless terminal downlink control information comprising an offset foruse in determining where in an uplink frame a response regarding datasent in the downlink frame should be placed.
 15. The method of claim 14,further comprising: transmitting in an uplink frame a response regardingdata sent in the downlink frame, the response being placed in the uplinkframe based on the location within the downlink frame at which thedownlink control information was located and the offset.
 16. The methodof claim 14, wherein where in the uplink frame the response should beplaced by is specified by the equationn _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾, wheren_(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ corresponds to the location in theuplink frame of the response; n_(CCE) corresponds to the location of thewireless terminal downlink control information; n_(PUCCH) _(_) _(offset)corresponds to the offset; and P₀ is an antenna port.
 17. A wirelessterminal configured to engage in wireless communication with thewireless base station, comprising: a processor circuit; and an uplinktransmission unit responsive to the processor circuit and configured totransmit an uplink radio signal to the wireless base station using afirst uplink resource; wherein the first uplink resource location isdetermined based on a resource allocation control signal received from abase station on a downlink resource and an offset specified as part ofthe resource allocation control signal.
 18. The wireless terminal ofclaim 17, wherein the wireless terminal is a Long Term Evolution (LTE)capable wireless terminal and the location of the first uplink resourcelocation n_(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ is given by: n_(PUCCH)^((1,{tilde over (p)}) ⁰ ⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾, where n_(CCE) is aminimum number of LTE control channel elements (CCE) used for sending ofthe corresponding resource allocation control signal; n_(PUCCH) _(_)_(offset) is the offset expressed in CCE units; and P₀ is an antennaport.
 19. The wireless terminal of claim 17, wherein the wirelessterminal is a Long Term Evolution (LTE) capable wireless terminal andthe location of the first uplink resource location n_(PUCCH)^((1,{tilde over (p)}) ⁰ ⁾ is given by:n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾ +n_(PUCCH) _(_) _(offset), where n_(CCE) is a minimum number of LTEcontrol channel elements (CCE) used for sending of the correspondingresource allocation control signal; n_(PUCCH) _(_) _(offset) is theoffset expressed in CCE units; P₀ is an antenna port; and N_(PUCCH) ⁽¹⁾is a parameter specified by an upper layer.
 20. The wireless terminal ofclaim 17, wherein the resource allocation control signal is a Long TermEvolution (LTE) downlink control information (DCI) signal comprisinginformation indicative of the offset.
 21. A wireless communicationsystem comprising: a wireless base station; and a wireless terminalconfigured to engage in wireless communication with the wireless basestation; wherein the wireless base station includes a downlinktransmission unit configured to transmit a first radio signal to thewireless terminal which includes a downlink allocation information, andthe wireless terminal includes an uplink transmission unit configured totransmit a first uplink control resource using a second radio signal,and wherein a location of the first uplink control resource in thesecond radio signal is determined based on a location of the downlinkallocation information in the first radio signal and an offset indicatedas part of the downlink allocation information.
 22. The wirelesscommunication system of claim 21, wherein the downlink allocationinformation is a Downlink Control Information (DCI) of Long TermEvolution (LTE).
 23. The wireless communication system of claim 21,further comprising another wireless base station and wherein thewireless terminal is further configured to engage in wirelesscommunication with the other wireless base station and wherein thewireless terminal transmits the first uplink control resource in thesecond radio signal such that the intended recipient is the otherwireless base station.
 24. The wireless communication system of claim21, further comprising another wireless base station and wherein thewireless terminal is further configured to engage in wirelesscommunication with the other wireless base station and wherein thewireless terminal transmits the first uplink control resource in thesecond radio signal such that the intended recipient is the wirelessbase station.